Multi Tech Systems Network Card BL Series User Manual

BL-Series  
Intelligent Data/Fax Modem  
User Guide  
 
Contents  
Chapter 1 - Introduction and Description  
1.1  
1.2  
1.3  
Introduction...................................................................................................................................... 8  
How To Use This Manual................................................................................................................. 8  
Modem Features ............................................................................................................................. 10  
1.3.1 2834 Series Features................................................................................................................ 10  
1.3.2 1932 Series Features................................................................................................................ 10  
1.3.3 1432 Series Features................................................................................................................ 11  
Fax Features ................................................................................................................................... 11  
Technical Specifications .................................................................................................................. 12  
Power .............................................................................................................................................. 16  
Modem LED Indicators .................................................................................................................... 16  
Controls on PC Board ..................................................................................................................... 17  
1.4  
1.5  
1.6  
1.7  
1.8  
Chapter 2 - Installation and Connection  
2.1  
2.2  
What is in Your Modem Package? .................................................................................................. 20  
Installation ....................................................................................................................................... 21  
2.2.1 Safety Warnings........................................................................................................................ 21  
2.2.2 Installation Procedure ............................................................................................................... 21  
2.2.3 Cabling Procedure (MT1432BL/BLI, MT1932BL/BLI, and MT2834BL/BLI) .............................. 21  
2.2.4 Cabling Procedure (MT1432BLK and MT2834BLK) ................................................................. 23  
Loading Trio DataFAX Software ...................................................................................................... 24  
Is Your Modem Ready for Use? ...................................................................................................... 26  
2.3  
2.4  
Chapter 3 - Software Configuration and Modem Basics  
3.1  
3.2  
Introduction...................................................................................................................................... 28  
Serial Port Limitations ..................................................................................................................... 28  
3.2.1 How Can You Identify Your UART Type? .................................................................................. 28  
3.2.2 The 16550 UART and Windows 3.1.......................................................................................... 29  
Configuring Your Software............................................................................................................... 29  
3.3.1 ConfiguringSoftware for Your Modem ....................................................................................... 29  
PC Initialization Strings ................................................................................................................... 30  
3.4.1 Changing Default Parameters................................................................................................... 30  
3.4.2 Other Parameters ..................................................................................................................... 30  
Macintosh Initialization .................................................................................................................... 31  
Configuring Software for Your Computer ......................................................................................... 31  
3.6.1 Configuring Software for the Remote System ........................................................................... 31  
3.6.2 Terminal Emulation ................................................................................................................... 31  
3.6.3 File Transfer Protocols .............................................................................................................. 32  
When to Disable Data Compression ............................................................................................... 32  
3.7.1 Disabling Error Correction......................................................................................................... 32  
Modem Basics ................................................................................................................................. 33  
3.8.1 Simple Operations .................................................................................................................... 33  
The Answer/Originate - Voice/Data Toggle Switch .......................................................................... 33  
3.3  
3.4  
3.5  
3.6  
3.7  
3.8  
3.9  
iii  
 
Chapter 4 - Manual Dial and Automatic Answer  
4.1  
4.2  
4.3  
4.4  
4.5  
4.6  
4.7  
4.8  
4.9  
4.10  
4.11  
Introduction...................................................................................................................................... 36  
Dialing/On-Line/Answering .............................................................................................................. 36  
Automatic Leased Line Restoral Operation ..................................................................................... 37  
Manual Dial Backup Call Termination .............................................................................................. 37  
Dial Backup and Leased Line Restoral ........................................................................................... 37  
Dial-Up Operation............................................................................................................................ 38  
Manual Call Origination ................................................................................................................... 38  
Automatic Answering ....................................................................................................................... 39  
Manual Answering ........................................................................................................................... 39  
Handshaking Details ....................................................................................................................... 40  
Call Termination ............................................................................................................................... 40  
Chapter 5 - Command Mode  
5.1  
Introduction...................................................................................................................................... 42  
5.1.1 AT Command Editing ................................................................................................................ 42  
5.1.2 Functional Modes...................................................................................................................... 43  
Summary of AT Commands............................................................................................................. 44  
Result Codes ................................................................................................................................... 47  
Dialing Commands .......................................................................................................................... 49  
5.4.1 Dialing Action Commands ......................................................................................................... 49  
5.4.2 Dial Modifier Commands ........................................................................................................... 50  
5.4.3 Phone Number Memory Commands......................................................................................... 53  
5.4.4 Configuration and Default Storage Commands ........................................................................ 54  
5.4.5 Command Response (Result Code) Commands ...................................................................... 56  
5.4.6 Phone Line Conditioning Commands........................................................................................ 58  
5.4.7 RS-232C Interface Control Commands .................................................................................... 61  
5.4.8 Error Correction Commands ..................................................................................................... 63  
5.4.9 Flow Control Commands .......................................................................................................... 66  
5.4.10 Compression, Error Correction, Flow Control, Pass-Through and Pacing Commands ............ 69  
5.4.11 Speed Conversion Commands ................................................................................................. 70  
5.4.12 Immediate Action Commands ................................................................................................... 73  
5.4.13 Line Probe Commands (2834 Series only) ............................................................................... 75  
5.2  
5.3  
5.4  
Chapter 6 - S-Registers  
6.1  
6.2  
Introduction...................................................................................................................................... 78  
Reading and Assigning S-Register Values ...................................................................................... 85  
6.2.1 Examples of Assigning Values .................................................................................................. 85  
6.2.2 Examples of Reading Values .................................................................................................... 85  
AT Command and S-Register Summary ......................................................................................... 86  
6.3  
Chapter 7 - Callback Security and Remote Configuration  
7.1  
7.2  
7.3  
Introduction...................................................................................................................................... 88  
Callback Feature Description .......................................................................................................... 88  
Remote Configuration Description................................................................................................... 89  
7.3.1 Initial Setup Procedures for Callback and Remote Configuration. ............................................ 89  
7.3.2 Remote Configuration Procedures ............................................................................................ 92  
Remote Configuration and Callback Security AT Commands ......................................................... 93  
Remote Configuration/Callback Security S-Registers ..................................................................... 95  
7.4  
7.5  
iv  
 
Chapter 8 - Modem Testing  
8.1  
8.2  
8.3  
8.4  
8.5  
8.6  
8.7  
8.8  
8.9  
Introduction...................................................................................................................................... 98  
Local Analog Loopback Test/V.54 Loop 3 ........................................................................................ 99  
Digital Loopback Test/V.54 Loop 2 (Local/Manual).......................................................................... 100  
Digital Loopback Test/V.54 Loop 2 (Remote/Automatic) ................................................................. 101  
Back-to-Back Test ........................................................................................................................... 102  
Synchronous Mode Testing ............................................................................................................. 103  
Local Analog Loopback Test (Synchronous Mode) ......................................................................... 103  
Digital Loopback Test (Local/Manual) (Synchronous Mode) ........................................................... 104  
Digital Loopback Test (Remote/Automatic) (Synchronous Mode) ................................................... 105  
Chapter 9 - DIP-Switch Settings  
9.1  
9.2  
9.3  
9.4  
Introduction...................................................................................................................................... 108  
DIP-Switch Option Settings ............................................................................................................. 109  
Speaker Volume Control ................................................................................................................. 114  
Recording Option Configurations .................................................................................................... 115  
Chapter 10 - Warranty, Service and Tech Support  
10.1  
10.2  
Introduction...................................................................................................................................... 118  
Limited Warranty ............................................................................................................................. 118  
10.2.1 On-line Warranty Registration ................................................................................................... 118  
10.3  
Tech Support ................................................................................................................................... 119  
10.3.1 Recording Modem Information .................................................................................................. 119  
10.4  
10.5  
Service ............................................................................................................................................ 119  
The Multi-Tech BBS......................................................................................................................... 120  
10.5.2 Upgrading the MultiModem ...................................................................................................... 121  
10.5.3 Using FlashPro to Upgrade Modem Firmware .......................................................................... 121  
10.6  
10.7  
10.8  
About Multi-Tech’s Internet Presence .............................................................................................. 121  
About the Multi-Tech Fax-Back Service .......................................................................................... 121  
About Ordering Accessories............................................................................................................ 122  
Appendixes  
Appendix A - Troubleshooting....................................................................................................................... 124  
Appendix B - ASCII Character Code/Hex/Decimal Conversion Chart .......................................................... 129  
Appendix C - Dial Pulse and Tone-Dial Frequencies.................................................................................... 130  
Appendix D - Command Summary............................................................................................................... 131  
Appendix E - DIP-Switch Summary ............................................................................................................. 140  
Appendix F - S-Register Summary .............................................................................................................. 143  
Appendix G - Result Code Summary ........................................................................................................... 145  
Appendix H - V.25bis Operation ................................................................................................................... 147  
Appendix I - MultiModemBL Cables ............................................................................................................. 154  
Appendix J - RS-232C Interface Specifications ........................................................................................... 156  
Appendix K - Regulatory Information ........................................................................................................... 160  
Index  
v
 
vi  
 
Chapter 1 - Introduction and Description  
 
MultiModemBL User Guide  
1.1 Introduction  
Welcome to the world of data communications. You have acquired one of the finest intelligent  
desktop data/fax modems available today, the MultiModemII BL series modem, from Multi-Tech  
Systems. This User Guide covers various models within the BL series, and unless otherwise noted,  
all content should be considered relevant to all models.  
Your MultiModem provides data communication at the following rates:  
Model  
Baud Rate  
MT2834BL Series  
MT1932BL Series  
MT1432BL Series  
33,600 - 14,400 bps (*Enhanced V.34/V.32bis)  
19,200 - 14,400 bps (V.32 terbo/V.32bis)  
14,400 - 300 bps (V.32 bis)  
*Note enhancements on V.34 code (33.6K/31.2K) is awaiting formal ITU approval; the ITU study group 14 has agreed on  
the technical side of the proposal, with formal approval expected at the next ITU meeting in Geneva.  
The MultiModem also provides other prevalent data communications standards and includes dial  
backup with automatic lease line restoration, adaptive protocol enhancing used in typical Unix® batch  
file transfers and support for IBM's AS/400TM and WindowsTM environments.  
1.2 How To Use This Manual  
This manual is divided into ten chapters. While viewing in Acrobat ReaderTM you can click on blue  
text to jump to the section of the manual it references. Red, bold text indicates a hyperlink to the  
Internet. If you have a Web browser active on your system, click on these text links to open the  
browser and go to the referenced site. The information contained in each chapter and appendix is as  
follows:  
Chapter 1 - Introduction and Description  
This chapter begins with a short introduction, followed by a guide (which you are now reading) to the  
use of this manual. There is a discussion about what components you can expect in your modem  
package. We then provide a more detailed description of the modem, including the modem’s  
technical specifications. Chapter 1 includes sections covering power, LED indicators and a brief  
summary of PC board controls. (Chapter 9 covers switch settings more thoroughly.)  
Chapter 2 - Installation and Connection  
Chapter 2 covers the procedure for connecting the modem to your computer and to the phone line.  
Details are given, supported by illustrations on the modem's back panel connections as a guide to  
install your modem to the point of operation. In addition, this chapter guides you through the  
installation of Trio, the communications software included with your modem.  
Chapter 3 - Software Configuration and Modem Basics  
Chapter 3 documents communication software configuration recommended specifically for the  
MultiModem. Other issues covered include setting up initialization strings, changing default  
parameters, configuring software for the remote system and file transfer protocols.  
Chapter 4 - Manual Dial and Automatic Answer  
Chapter 4 covers some modem operations, but delays discussion on Command Mode operation until  
Chapter 5. Automatic Leased Line Restoration, Dial backup, Manual Dial Mode, and Answer Mode  
operation are covered in detail, as well as the handshaking procedures employed between two  
modems in an auto-answer application.  
8
 
Chapter 1 - Introduction and Description  
Chapter 5 - AT Command Mode Operation  
Chapter 5 may be the most important chapter of this manual. It begins with an introduction and  
discussion on Command Mode fundamentals. A flow chart is provided to illustrate Command Mode  
and On-Line Mode operation and the methods used in each mode. Next, there is a summary of the  
modem’s commands and responses. We then go into a detailed explanation of each modem  
command, providing examples where applicable.  
Chapter 6 - S-Registers  
Chapter 6 covers the modem's S-Registers, which enable the user to establish, read, and modify  
various modem options. All of the S-Registers are charted and explained, followed by instructions on  
accessing the S-Registers and reading or changing their values.  
Chapter 7 - Callback and Remote Configuration  
Chapter 7 documents instructions on how to operate the modem's Callback and Remote  
Configuration features; and the usage of LOGIN Passwords, Set-Up Passwords and Remote Escape  
Characters as network management tools.  
Chapter 8 - Testing Your Modem  
Chapter 8 covers the modem's built-in test features. These are: Power-on Self Test, Back-To-Back  
Test, Local Analog Loopback, Digital Loopback and Remote Digital Loopback Tests. We have  
included a description of each test and how to use each test procedure.  
Chapter 9 - DIP-Switches  
Chapter 9 covers the modem’s printed-circuit board options. Sixteen DIP-Switch settings and the  
modem's speaker volume control are explained in detail, including all default settings.  
Chapter 10 - Warranty, Service & Technical Support  
Chapter 10 provides statements on your five-year warranty, instructions for getting modems serviced  
at the factory, the procedure for downloading firmware upgrades via FlashROM, information about  
Multi-Tech's Bulletin Board Service (BBS), a section on receiving technical support via the  
CompuServe/Internet forums and information on Multi-Tech's Fax-Back Service.  
Appendixes  
There are also several appendices at the end of this manual, most of which repeat information  
contained in the chapters, but in a more condensed form. These appendices can be used as a quick  
reference.  
Appendix A - Troubleshooting  
Appendix B - ASCII/HEX/Decimal Conversion Chart  
Appendix C - Pulse Dial and Tone-Dial Frequencies  
Appendix D - AT Command Summary  
Appendix E - DIP Switch Summary  
Appendix F - S-Register Summary  
Appendix G - Result Code Summary  
Appendix H - V.25bis Operation  
Appendix I - Cabling Diagrams  
Appendix J - RS-232 Interface Specifications  
Appendix K - Regulatory Information  
9
 
MultiModemBL User Guide  
1.3 Modem Features  
The MultiModem BL Series modem connections can be made on Public Switched Telephone  
Networks (PSTNs) and/or point-to-point 2-wire and 4-wire leased telephone type circuits.  
Your modem offers interactive automatic dialing, as well as Command Mode option configuration.  
You may store up to ten command line/telephone numbers, of up to 60 characters each, in the  
modem’s nonvolatile memory. The modem pulse or tone dials, and recognizes dial tones and busy  
signals for reliable call-progress detection. The modem can detect AT&T calling card tones. It is  
FCC-Registered for connection to telephone networks without any Data Access Arrangements  
(DAA’s).  
Your modem also features Callback Security to protect networks from unauthorized use, and to  
manage phone line costs. By using the modem’s phone number and password directory, a host site  
can, upon receipt of a call, callback to a remote site at a predetermined number.  
Remote Configuration permits you to assist users at remote sites, saving you the time and trouble of  
site visits and preventing misinterpretation of configuration instructions.  
1.3.1  
2834 Series Features  
Your MT2834BL modem meets the proposed Enhanced V.34 ITU standard for data signalling rates  
as high as 33.6/31.2K bps in full duplex mode. Enhanced V.34 is an extension of V.32/V.32bis/V34  
standards, and supports and is compatible with those features, including EIA extended Automode;  
adaptive line probing; automatic symbol rate and carrier frequency during start-up; and retrain and  
rate renegotiation (in 2400 bps increments).  
The major application for the MT2834BL is in 4-wire leased line networks with the addition of dial  
backup capability. With this capability, the dial-up feature saves any down time if the leased line fails.  
Since the MT2834BL operates according to ITU V.34 modulation, it can operate full-duplex over two  
wires, so that the dial backup mode performs the same throughput as the leased line.  
The MT2834BL features ITU V.42 error correction and V.42bis data compression, providing 100%  
error-free data transmission. V.42 error correction incorporates MNP( Classes 3 and 4, and LAP-M.  
You may select V.42bis data compression for 4-1 throughput, or MNP Class 5 for 2-1 throughput.)  
1.3.2  
1932 Series Features  
Your MT1932BL modem is designed according to the American Telephone and Telegraph (AT & T)  
V.32terbo de facto standard for data signalling rates as high as 19.2/16.8K bps full-duplex mode.  
V.32 terbo supports and is compatible with all V.32 and V.32bis features including EIA extended  
Automode, the V.32 start-up sequence, and V.32bis retrain and rate renegotiation.  
The major application for the MT1932BL is in 4-wire leased line networks with the addition of dial  
back-up capability. With this capability, the dial-up feature saves any down time if the leased line  
fails.  
The MT1932BL is AT command set compatible and incorporates a number of capabilities beyond the  
basics of V.32terbo operation. Other capabilities include CCITT V.25bis standard for synchronous  
dialing, compatibility with CCITT V.42 error correction and V.42bis data compression in which data  
communication speeds can approach 78,600 bps (depending on the file content and the receiving  
modem’s capability) and the data sent will be 100% error free. V.42 error correction incorporates both  
MNP Classes 3, 4 and LAPM. Data compression can be V.42bis for 4 to 1 throughput improvement  
or MNP Class 5 for 2 to 1 throughput.  
10  
 
Chapter 1 - Introduction and Description  
1.3.3  
1432 Series Features  
Your MT1432BL modem is designed according to the international CCITT V.32bis specification for  
data signalling rates as high as 14.4K bps in full-duplex mode.  
The major application for the MT1432BL is in 4-wire leased line networks (replacing traditional V.29/  
9600 bps & V.33/14,400 bps modems) with the addition of dialback-up capability. With this  
capability, the dial-up feature saves any down time if the leased line fails. Since the MT1432BL  
operates according to CCITT V.32bis modulation, it can operate full-duplex over two wires, so that  
the dial back-up mode performs the same throughput as the leased line.  
The MT1432BL is AT command set compatible and incorporates a number of capabilities beyond the  
basics of V.32bis operation. Other capabilities include CCITT V.25bis synchronous dialing,  
compatibility with CCITT V.42 error correction and V.42bis data compression in which data  
communication speeds approach 57,600 bps (depending on the file content and the receiving  
modem’s capability) and the data sent will be 100% error free.  
1.4 Fax Features  
Your modem meets the ITU V.17 standard for sending and receiving faxes. When linked to a  
compatible fax machine or modem, it can transmit faxes at 14,4 K bps. It also meets the ITU’s Group  
3 Designation for sending and receiving faxes at 9600 bps; and Group 2 Designation for sending and  
receiving faxes at 4800 bps. The modem is also downward-compatible with modems to speeds as  
low as 300 bps, so it can send and receive faxes with any fax machine in the world.  
11  
 
MultiModemBL User Guide  
1.5 Technical Specifications  
Your data/fax modem meets the specifications listed below:  
Tradename  
MultiModemIITM  
Model Numbers  
2834 Series:  
1932 Series:  
1432 Series:  
MT2834BL, MT2834BLI, MT2834BLK  
MT1932BL, MT1932BLI, MT2834BL-MAC  
MT1432BL, MT1432BLI, MT21432BLK  
Data Rates (modem)  
2834 Series:  
33,600, 31,200, 28,800, 26,400, 24,000, 21,600, 19,200, 16,800,  
14,400, 12,000, 9600, 7200, 4800, 2400, 1200, 0-300 bps  
1932 Series:  
19,200, 16,800, 14,400, 12,000, 9600, 7200, 4800, 2400, 1200,  
0-300 bps  
1432 Series:  
Data Rates (fax)  
All Models:  
14,400, 12,000, 9600, 7200, 4800, 2400, 1200, 0-300 bps  
14,400, 9600, 7200, 4800 bps  
Data Format  
2834 Series:  
Serial, binary, asynchronous at 0-300, 1200, 2400, 4800, 7200,  
9600, 12,000, 14,400, 16,800, 19,200, 21,600, 24,000, 26,400,  
28,800, 31,200, 33,600 bps; synchronous at 1200, 2400, 4800,  
7200, 9600, 12,000, 14,400, 16,800, 19,200, 21,600, 24,000, 26,400,  
28,800, 31,200, 33,600 bps  
1932 Series:  
1432 Series:  
Serial, binary, asynchronous at 0-300, 1200, 2400, 4800, 7200,  
9600, 12,000, 14,400, 16,800, 19,200 bps; synchronous at 1200,  
2400, 4800, 7200, 9600, 12,000, 14,400, 16,800, 19,200 bps  
Serial, binary, asynchronous at 0-300, 1200, 2400, 4800, 7200,  
9600, 12,000, 14,400 bps; synchronous at 1200, 2400, 4800, 7200,  
9600, 12,000, 14,400 bps  
Compatibility  
2834 Series:  
ITU V.42bis, V.42, Pending ITU Enhanced V.34 approval, ITU V.34,  
ITU V.32bis, V.32, V.21*, V.22bis, V.22, V.23*,V.25bis, *Bell 212A  
and 103/113, ITU V.17, Group 3 T.4, T.30 and EIA TR-29 Class 2  
(*Bell 212A and 103/113 domestic models only; *V.21/V.23 Int'l  
models only)  
1932 Series:  
1432 Series:  
CCITT V.42bis, V.42, AT&T V.32terbo, CCITT V.32bis, V.32, V.21*,  
V.22bis, V.22, V.23*, V.25bis, Bell 212A and 103/113, CCITT V.17,  
Group 3 T.4, T.30 and EIA TR-29 Class 2 (* V.21/V.23 Int’l models  
only)  
CCITT V.42bis, V.42, CCITT V.32bis, V.32, V.21*, V.22bis, V.22,  
V.23*, V.25bis, Bell 212A and 103/113*, CCITT V.17, Group 3 T.4,  
T.30 adn EIA TR-29 Class 2 (* Bell 212A and 103/113 domestic  
models only; * V.21/V.23 Int’l models only)  
Error Correction  
All models:  
V.42 (LAP-M or MNP 3 & 4) error correction  
12  
 
Chapter 1 - Introduction and Description  
Data Compression  
All models:  
V.42bis, (4:1 throughput) or MNP 5 (2:1 throughput) data  
compression  
Speed Conversion  
2834 and 1932 Series:  
Serial port data rates adjustable to 300, 1200, 2400, 4800, 9600,  
19,200, 38,400, 57,600 and 115,200 bps  
1432 Series:  
Serial port data rates adjustable to 300, 1200, 2400, 4800, 9600,  
19,200, 38,400, and 57,600 bps  
Flow Control Options  
All models:  
Xon/Xoff, Hardware RTS/CTS, ENQ/ACK, Unix-to-Unix Copy  
Protocol (UUCP) "Spoofing"  
Mode of Operation  
All models:  
Full duplex over both dial-up lines and 2- or 4-wire leased lines;  
automatic Dial backup on separate lines in leased line operation;  
automatic or manual dialing, automatic or manual answer  
Intelligent Features  
All models:  
Fully “AT command” compatible, microprocessor controlled remote  
configuration, EIA extended Automode, adaptive line probing,  
automatic symbol rate and carrier frequency during start-up, retrain  
and rate renegotiation, autodial, redial, repeat dial, dial linking, pulse  
or tone dial, dial tone detection, dial pauses, call status display, auto-  
parity and data rate selection, keyboard-controlled modem options,  
nonvolatile memory and on-screen displays for modem option  
parameters and up to ten telephone numbers/command lines of up  
to 60 digits each, help menus  
Command Buffer  
All models:  
60 characters  
Modulation  
2834 Series:  
Trellis Coded Modulation (TCM) at 33,600, 31,200, 28,800, 26,400,  
24,000, 21,600, 19,200, 16,800, 14,400, 12,000 and 9600 bps,  
Quadrature Amplitude Modulation (QAM) at 9600 (non-trellis), 4800  
and 2400 bps, PSK at 1200 bps, FSK at 300 bps  
1932 Series:  
1432 Series:  
Trellis Coded Modulation (TCM) at 19,200, 16,800, 14,400, 12,000  
and 9600 bps, Quadrature Amplitude Modulation (QAM) at 9600  
(non-trellis), 4800 and 2400 bps, PSK at 1200 bps, FSK at 300 bps  
Trellis Coded Modulation (TCM) at 14,400, 12,000 and 9600 bps,  
Quadrature Amplitude Modulation (QAM) at 9600 (non-trellis), 4800  
and 2400 bps, PSK at 1200 bps, FSK at 300 bps  
Fax Modulations  
All models:  
V.21CH2 FSK at 300 bps, V.27ter DPSK at 4800 and 2400 bps,  
V.29 QAM at 9600 and 7200 bps, V.17 TCM at 14400, 12000, 9600,  
and 7200 bps  
13  
 
MultiModemBL User Guide  
Fax Carrier Frequencies  
All models:  
V.21CH2 (Half Duplex)  
1650Hz Mark, 1850Hz Space for Transmit Originate  
1650Hz Mark, 1850Hz Space for Transmit Answer  
V.27ter 1800Hz Originate/Answer  
V.29 QAM 1700Hz Originate/Answer  
V.17 TCM 1800Hz Originate/Answer  
Lease Line Restoral  
All models:  
When in dial backup mode, modem attempts leased line restoral  
periodically (controlled by S-Register S18 setting)  
Carrier Frequencies  
2834 Series:  
1800 Hz V.32/V.32bis/V.34/Enhanced V.34--33.6K/31.2K/28.8K/  
26.4K/24K/21.6K/19.2K/16.8K/14.4K/12K/9.6K/7.2K/4.8K  
1932 Series:  
1800 Hz V.32/V.32bis/V.32terbo/19.2K/16.8K/14.4K/12K/9.6K/7.2K/  
4.8K  
1432 Series:  
1800 Hz V.32/V.32bis/14.4K/12K/9.6K/7.2K/4.8K  
Carrier Frequencies - 2400 & 1200 bps (V.22bis/V.22 or Bell 212A Standard)  
All models:  
Transmit Originate:  
Transmit Answer:  
Receive Originate:  
Receive Answer:  
1200 Hz  
2400 Hz  
2400 Hz  
1200 Hz  
Carrier Frequencies - 300 bps (Bell Standard)  
All models:  
1270 Hz Mark, 1070 Hz Space for Transmit Originate  
2225 Hz Mark, 2025 Hz Space for Receive Originate  
2225 Hz Mark, 2025 Hz Space for Transmit Answer  
1270 Hz Mark, 1070 Hz Space for Receive Answer  
Carrier Frequencies - V.21  
All models:  
980 Hz Mark, 1180 Hz Space for Transmit Originate  
1650 Hz Mark, 1850 Hz Space for Transmit Answer  
650 Hz Mark, 1850 Hz Space for Receive Originate  
980 Hz Mark, 1180 Hz Space for Receive Answer  
Carrier Frequencies - V.23  
All models:  
390 Hz Mark, 450 Hz Space for Transmit Originate  
1300 Hz Mark, 2100 Hz Space for Transmit Answer  
1300 Hz Mark, 2100 Hz Space for Receive Originate  
390 Hz Mark, 450 Hz Space for Receive Answer  
Transmit Level  
All models:  
-11dBm (dial-up), -9 or -15 dBm (leased-line); dBm level selectable  
with DIP-Switch #3 in leased line setting; -10dBm (dial-up)*, -13 dBm  
(leased-line)*  
*BLK models Only  
Frequency Stability  
All models:  
±0.01%  
14  
 
Chapter 1 - Introduction and Description  
Receiver Sensitivity  
All models:  
-43 dBm under worst case conditions  
AGC Dynamic Range  
All models:  
43 dB  
Interface  
All models:  
EIA RS-232C/ITU V.24  
Connectors  
BL models:  
One DB-25 RS-232C connector; three RJ11 for phone line, dial-up  
and leased line; power.  
BLK models:  
One DB-25 RS-232C connector; two BT plugs for dial-up and leased  
line; power  
Diagnostics  
All models:  
Power-on Self Test, Local Analog Loop, Local Digital Loop, Remote  
Digital Loop, Back-to-Back Test.  
Indicators  
All models:  
LEDs for Transmit Data, Receive Data, Carrier Detect, Speed  
Indicators, Off Hook, Terminal Ready, Error Correction, Fax, and  
Error  
Controls  
All models:  
Toggle switches for Voice/Data with Originate or Answer, Power On/  
Off; and DIP Switches for various modem options.  
Speaker  
All models:  
Speaker for call progress monitoring  
0° to 50° C (32° to 120° F)  
Operating Temperature  
All models:  
Power Requirements  
All models:  
115 Volts AC, 60Hz, 0.3amp (2-prong outlet-mounted transformer)  
240V/50Hz optional (International).  
Dimensions  
All models:  
6.150" x 9.00" x 1.375"  
15.6 cm x 22.9 cm x 3.5 cm  
Weight  
All models:  
1.6 pounds/0.72 Kg (without transformer)  
2.6 pounds/1.18Kg (with transformer)  
Limited Warranty  
All models:  
Five Years  
15  
 
MultiModemBL User Guide  
1.6 Power  
Power is supplied through an AC power transformer terminated with a standard two-prong plug. The  
transformer supplies low voltage AC to the modem, and plugs into any conventional 115 volt AC, 60  
Hz, two-prong power outlet (240 volts AC, 50Hz, .3 Amp for International modems). The power  
transformer supplied with the modem is the only one that should be used. Use of any other  
transformer could cause damage to the modem. A Power On/Off switch is located on the back of the  
modem.  
1.7 Modem LED Indicators  
The MultiModem diagnostic LED indicators are shown in Figures 1-1a, 1-1b, and 1-1c.  
Figure 1-1a. MT2834 LED Display  
Figure 1-1b. 1932 LED Display  
Figure 1-1c. MT1432 LED Display  
(SD) Send (Transmit) Data. This LED blinks when data is being transmitted, on for a space, off for a  
mark. The state of this LED matches the TD circuit on Pin 2 of the RS-232C/V.24 interface.  
(RD) Receive Data. This LED blinks when data is being received, on for a space, off for a mark. The  
state of this LED matches that of the RD circuit on Pin 3 of the RS-232C/V.24 interface.  
(CD) Carrier Detect. This LED is lit when a valid carrier tone has been detected.  
2834 Models Only:  
When the modem is connected at 33,600 bps, the 28.8 LED rapidly blinks at approximately 5  
blinks per second.  
When the modem is connected at 31,200 bps, the 28.8 LED blinks slowly at approximately 1  
blink per second.  
(28.8) 28,800 bps. (2834 models only) This LED is lit when the modem is connected at 28,800 bps.  
Note: if the modem falls back to 26.4K bps while in V.34 mode, both the 28.8 and 24.0 LEDs light.  
16  
 
Chapter 1 - Introduction and Description  
(24.0) 24,000 bps. (2834 models only). This LED is lit when the modem is connected at 24,000 bps.  
Note: if the modem falls back to 21.6K bps while in V.34 mode, both the 24.0 and 19.2 LEDs light.  
(19.2) 19,200 bps. (2834 and 1932 models only) This LED is lit when the modem is connected at  
19,200 bps.  
(14.4) 14,400 bps. This LED is lit when the modem is connected at 14,400 bps. Note: if the modem  
falls back to 12,000 bps while in V.32bis mode, both the 14.4 and 96 LEDs light.  
(96) 9600 bps. This LED is lit when the modem is connected at 9600 bps.  
(24) 2400 bps. This LED is lit when the modem is connected at 2400 bps.  
(12) 1200 bps. (1432 models only) This LED is lit when the modem is connected at 1200 bps.  
(OH) Off Hook. This LED is lit when the phone line is "off hook". This occurs when the modem is  
dialing, on-line, or answering a call. This LED also flashes when the modem is pulse dialing in  
Command mode.  
(TR) Terminal Ready. When the TR LED is lit, the modem is permitted to answer an incoming call.  
When it goes off, a connected modem will disconnect. The state of the TR LED matches that of the  
DTR circuit on Pin 20 of the RS-232C/V.24 interface.  
(EC) Error Correction. This LED is lit when the modem is set for V.42 error correction, and flashes on  
and off when data compression is activated.  
(FX) FAX. This LED is lit when the modem is connected in FAX mode.  
(ERR) ERROR. When this LED is lit, either the leased line is down and the modem is in dial backup  
mode, or else the self-test has failed.  
1.8 Controls on PC Board  
The MultiModem is designed on a single printed circuit (PC) board. This board contains one 16-  
position DIP-Switch (numbered 1-16). The DIP-Switches are accessible through a cut-out on the side  
of the modem. There is also a knob which is used to adjust the speaker volume. This knob is  
accessible through the modem's rear panel. The sixteen DIP-Switches control various modem  
options or set default values for Command Mode operation. There is a difference in how several of  
the switches operate depending on whether you are in synchronous or asynchronous mode. Refer to  
the switch label on the bottom of the modem for an exact list of the switch functions in asynchronous  
and synchronous operation. Chapter 9 of this manual also provides detailed instructions on  
configuring all of the modem's PC board options.  
17  
 
MultiModemBL User Guide  
18  
 
Chapter 2 - Installation and Connection  
 
MultiModemBL User Guide  
2.1 What is in Your Modem Package?  
Your MultiModem is made up of many components. Make sure you have them all before trying to  
operate your modem.  
MADE IN U.S.A  
MADE IN U.S.A  
Figure 2-1. Unpacking (MT2834BL shown)  
Your package should include:  
MT2834BL, MT1932BL or MT1432BL data/fax modem  
RJ-11 telephone cord or BS-6312 Plug (UK models)  
AC Power Transformer  
One (1) Quick Start Guide  
One (1) software CD (TrioTM data communications and fax software)  
This User Guide (on diskette)  
If any of these items are missing, please refer to the Chapter 10 for information on contacting Tech  
Support.  
20  
 
Chapter 2 - Installation and Connection  
2.2 Installation  
The installation of the modem consists of making the physical connections necessary to render the  
modem functional with your computer. This includes making the proper serial, phone line, and power  
connections. Unless otherwise noted, these instructions apply to all models of the BL series.  
2.2.1  
Safety Warnings  
1
2
Never install telephone wiring during a lightning storm.  
Never install telephone jacks in wet locations unless the jack is specifically designed for wet  
locations.  
3
Never touch uninsulated telephone wires or terminals unless the telephone line has been  
disconnected at the network interface.  
4
5
Use caution when installing or modifying telephone lines.  
Avoid using a telephone (other than a cordless type) during an electrical storm. There may be a  
remote risk of electrical shock from lightning.  
6
7
Do not use the telephone to report a gas leak in the vicinity of the leak.  
Ports which are connecting to other apparatus are defined as SELV. To ensure conformity with  
EN 41003, ensure that these ports are only connected to the same type on other apparatus.  
2.2.2  
Installation Procedure  
The following procedures will guide you through the physical connections required to make your  
modem operational. Software loading is covered later in this guide.  
Note: There are two procedures in this section. The first details cabling for domestic (BL) and  
international (BLI) models. The second details cabling for BABT (BLK) models only. Please follow the  
procedure that matches your model.  
2.2.3  
Cabling Procedure (MT1432BL/BLI, MT1932BL/BLI, and  
MT2834BL/BLI)  
Step Procedure  
1
Verify that the settings for DIP-Switch #5 and DIP-Switch #10 match those of your system  
configuration.  
The 16-position DIP-Switch (numbered 1-16) is accessible through a cut-out on the right side (as  
the LEDs are facing you) of the modem chassis. For a full description of all DIP-Switch Settings,  
refer to Chapter 9.  
DIP-Switch  
Condition Effect  
#5  
UP*  
Selects Answer mode  
DOWN  
UP*  
Selects Originate mode  
#10  
Selects Dial-Up operation  
Selects Lease Line operation  
DOWN  
* indicates Factory Default setting  
2
3
Verify that the ON/OFF switch at the rear of the modem to the OFF (Down) position.  
Connect the modem to either a dial-up line or lease-line.  
To connect the modem to a dial-up phone line, attach the RJ-11 telephone cord (provided with  
your unit) to the PSTN connector on the modem and to a dial-up wall jack. Refer to Figure 2-2.  
To connect the modem to a leased line, attach the RJ-11 telephone cord (provided with your unit)  
to the LEASE connector on the modem and to a leased line wall-jack. Refer to Figure 2-2.  
21  
 
MultiModemBL User Guide  
PHONE  
PSTN  
LEASE  
EIA RS232C  
ON  
OFF  
VOLUME  
POWER  
Figure 2-2. MultiModemBL/BLI Connections  
4
5
Attach the EIA RS-232C connector on the modem to the serial port on your computer or terminal  
with an RS-232 (or V.24) cable (you supply). Refer to Figure 2-2.  
To connect a telephone set to the modem (optional) plug one end of an RJ-11 phone cord into  
the PHONE connector on the modem, and plug the other end into your telephone. Refer to  
Figure 2-2.  
6
7
Attach the AC Power transformer provided with your unit to the POWER connector on the  
modem and to a live AC outlet. Refer to Figure 2-2.  
Note: Only apply power to the modem using the power transformer provided with your unit. Use  
of a power supply not designed for your unit could result in damage to your modem and will void  
the warranty.  
Apply power to the unit by setting the ON/OFF switch at the rear of the modem to the ON (Up)  
position. Refer to Figure 2-2.  
22  
 
Chapter 2 - Installation and Connection  
2.2.4  
Cabling Procedure (MT1432BLK and MT2834BLK)  
Step Procedure  
1
Verify that the settings for DIP-Switch #5 and DIP-Switch #10 match those of your system  
configuration.  
The 16-position DIP-Switch (numbered 1-16) is accessible through a cut-out on the right side (as  
the LEDs are facing you) of the modem chassis. For a full description of all DIP-Switch Settings,  
refer to Chapter 9.  
DIP-Switch  
Condition Effect  
#5  
UP*  
Selects Answer mode  
DOWN  
UP*  
Selects Originate mode  
#10  
Selects Dial-Up operation  
Selects Lease Line operation  
DOWN  
* indicates Factory Default setting  
Note 1: BLK models use pins 1 and 6 of the BS-6312 plug for two-wire lines. For four-wire lines,  
the modems use pins 1 and 6 to transmit and pins 2 and 5 to receive.  
Note 2: BABT regulations require that telecommunication cables must be connected to the  
modem prior to being connected to the network.  
2
3
Verify that the ON/OFF switch at the rear of the modem to the OFF (Down) position.  
Connect the modem to either a dial-up line or lease-line.  
To connect the modem to a dial-up phone line, attach the BS-6312 telephone cord (provided with  
your unit) to the PSTN connector on the modem and to a dial-up wall jack. Refer to Figure 2-3.  
To connect the modem to a leased line, attach the BS-6312 telephone cord (provided with your  
unit) to the LEASE connector on the modem and to a leased line wall-jack. Refer to Figure 2-3.  
PSTN  
LEASE  
EIA RS232C  
ON  
OFF  
VOLUME  
POWER  
Figure 2-3. MultiModemBLK Connections  
4
5
Attach the EIA RS-232C connector on the modem to the serial port on your computer or terminal  
with an RS-232 (or V.24) cable (you supply). Refer to Figure 2-3.  
Attach the AC Power transformer provided with your unit to the POWER connector on the  
modem and to a live AC outlet. Refer to Figure 2-3.  
Note: Only apply power to the modem using the power transformer provided with your unit. Use  
of a power supply not designed for your unit could result in damage to your modem and will void  
the warranty.  
23  
 
MultiModemBL User Guide  
2.3 Loading Trio DataFAX Software  
The following procedure will guide you through the installation of Trio DataFAX software. The  
procedure does not provide every screen or option in the process. The installation utility provides on-  
screen instructions for those elements that are not covered in this procedure. If you encounter  
problems during installation, refer to the Release Notes included on the Trio CD.  
1
Turn on your computer and insert the Trio CD into your CD-ROM drive. If you have autorun  
enabled, the Trio welcome screen will appear. If autorun is disabled, you can start the installation  
program by clicking double-clicking Setup16 or Setup32 from the root directory of the Trio CD.  
2
3
Click the Next ( ) icon to proceed with the default language, English, or select the desired  
language and click Next to proceed.  
Click Next to proceed with the default country, United States, or select the country in which you  
are installing and click Next to proceed. The Trio Welcome screen is displayed  
Note: If you have a sound card installed on your computer and wish to turn off the music portion  
of the Trio CD, you can click the Speaker ( ) icon to turn the sound off. Click Speaker again to  
turn it back on.  
4
Click Next. The following dialog is displayed:  
5
Click Trio... to continue. The following dialog box is displayed  
6
7
Click Install Trio... to continue. The Select Language dialog is displayed.  
Click OK to proceed with the default language, English, or select the desired language from the  
drop-down list and click OK. The License Agreement dialog is displayed.  
8
Read the license agreement, and click OK when you are finished. You are prompted to read  
important information.  
24  
 
Chapter 2 - Installation and Connection  
9
Click Yes to read the Release Notes. when you are finished, close the release notes dialog and  
the Trio Setup dialog is displayed.  
10 Click Complete Installation and the installation introduction is presented.  
11 Click Next Dialog and follow the on-screen instructions to load the software.  
Once the software has finished loading, the following dialog is displayed:  
12 Choose Manual Selection of Modem and Ports, then click Next Dialog. The following dialog is  
displayed:  
13 In the Com Port Selection group select the COM port, on which your modem is installed, from  
the drop-down list.  
14 In the Modem Type group select Class 2 Compatible from the drop-down list.  
25  
 
MultiModemBL User Guide  
15 Click Next Dialog. The Phone Numbers and Prefixes dialog is displayed.  
16 Follow the on-screen instructions and when you are finished, click Next Dialog. The following  
dialog is displayed:  
17 Click OK, Exit the Installation Program. The Trio Applications program group is displayed.  
Your Trio software is loaded. If you wish to begin using Trio right away, double click on the Trio  
DataFax Voice icon. Refer to the Release Notes for instructions.  
To quit Trio altogether, close the Trio Applications program group, and then click the Exit ( ) icon  
on the installation screen to exit the installation program.  
2.4 Is Your Modem Ready for Use?  
As soon as you have connected power to the modem, if you are an experienced modem user, you  
may simply want to check your modem’s settings for data compression, error correction, and so on.  
You may find that you can get moving quite quickly if you just issue an ATL5, ATL6 and an ATL7  
command. These commands list how your modem is currently configured. If you come across a  
setting you’re unsure of, refer to Chapter 5 and Chapter 6 for AT command and S-Register  
explanations and defaults.  
If you’re a novice, refer to Chapter 3 to learn about the basics of data communications.  
26  
 
Chapter 3 - Software Configuration and Modem Basics  
 
MultiModemBL User Guide  
3.1 Introduction  
Chapter 2 guided you through the installation of Trio communications software. If you are using a  
different software package, there are some points you should take into consideration. Since your  
communications software configuration is affected by the capabilities of your computer, this chapter  
begins with a discussion of the limitations of some serial ports and how to identify them. It then  
discusses communications configuration in general and recommends settings specifically for the  
MultiModem. The last section of this chapter walks you through the basics of using your modem.  
3.2 Serial Port Limitations  
When you configure your software, you need to consider how the hardware on both ends of the  
connection will affect the connection. Some serial ports, particularly those in older PC-compatible  
computers, may limit the performance of the modem. You should know if yours is one of them.  
The limiting factor is an integrated circuit called a Universal Asynchronous Receiver/Transmitter, or  
UART. All data from your modem flows through it. The UARTs typically used in PC-compatible  
computers are types 8250, 8250A, 16450, and 16550AFN. The 8250 is unreliable above 9,600 bps,  
and the 8250A and 16450 are unreliable above 19,200 bps. If the modem sends data to the UARTs  
above those speeds, the UARTs may not be able to process the data fast enough to keep from losing  
some of it. The 16550AFN, however, can safely handle data to 115,200 bps.  
When a modem communicates with V.42bis 4-to-1 compression enabled, it sends up to four times as  
much uncompressed data to the serial port as it receives compressed over the telephone line.  
Therefore, a modem communicating at 14,400 bps may require a serial port that can reliably transfer  
data at four times 14,400 bps, or 57,600 bps; at 19,200 bps it may require one that works reliably up  
to four times 19,200 bps, or 76,800 bps; and at 28,800 and 33,600 bps it may require one that works  
reliably up to a maximum of 115,200 bps. If your serial port cannot handle these speeds, we  
recommend that you replace your present serial card with one that has a 16550AFN UART or  
equivalent.  
Macintosh computers do not use UARTs. The Macintosh SE through IIfx models use a Zilog Z8530  
chip called a Serial Communications Controller, or SCC, that has a maximum speed of 57,600 bps.  
This speed can be compromised by other serial communications, including printer transmissions and  
Appletalk, the networking software that allows Macintoshes to share files. When Appletalk is active it  
controls all serial communications on the Macintosh. Because it gives priority to network  
communications, it may lose modem data at higher transmission speeds. Therefore, when Appletalk  
is active you risk losing data on serial port communications over 2400 bps, though most users can  
work up to 9600 bps without problems. Other activities that could cause the serial driver to drop bits  
at high speeds include the floppy disk driver formatting a disk, the CPU paging in or out in virtual  
memory mode, and the Mac IIci or IIsi running the on-board video in 8-bit mode. Therefore, for  
maximum communications speed on the Macintosh, we recommend as few concurrent activities as  
possible. To use V.42bis compression at 19,200 bps or faster, we recommend that you install a high  
speed serial port card. Newer Macintosh computers, such as the Quadra and Centris models,  
support serial port speeds up to 115,200 bps.  
3.2.1  
How Can You Identify Your UART Type?  
If you have MS-DOS 6.0 or later, you can find your UART type from a diagnostic program called  
MSD. To use it, type MSD at the DOS prompt. After the opening screen, select COM Ports.... The  
last line of the report tells you what type UART you have for each COM port. MSD does not  
distinguish between the 8250 and the 8250A. However, if you have an IBM AT or newer computer,  
you likely have an 8250A or 16450 UART installed, both of which are reliable to 19,200 bps. If you  
would like more detailed information about your UART than MSD can provide, you can download  
shareware UART identification programs from the IBM Communications Forum on CompuServe, or  
from a local BBS.  
28  
 
Chapter 3 - Software Configuration  
3.2.2  
The 16550 UART and Windows 3.1  
Windows 3.1 may cause a loss of data when communicating at high speed, even with a 16550 UART  
installed. Because Windows is multitasking—it switches between several programs running at the  
same time—it can make the serial port wait briefly while Windows performs other tasks. Meanwhile,  
incoming data can be lost. The older 8250A and 16450 UARTs can store data in a one-byte first in-  
first out (FIFO) buffer (a memory area in the UART in which the first bit in is the first out), but once  
the buffer is full, the data is lost. The 16550 has a 16-byte FIFO buffer, which accounts for much of its  
high speed. However, in Windows 3.1, the 16550’s FIFO buffer is disabled by default. To enable the  
buffer, use Notepad to open the SYSTEM.INI file in your Windows directory, and add the following  
line to the [386Enh] section:  
COMnFIFO=1  
where n is the number of the COM port the 16550 is installed on. For example, if the 16550 is  
installed on COM2, the line should be:  
COM2FIFO=1  
After you save SYSTEM.INI you must restart Windows for the change to take effect.  
However, there is another problem when the FIFO buffer is enabled: Windows cannot recognize the  
COM port because of a bug in the Windows 3.1 serial port driver, COMM.DRV. The only way around  
this problem is to replace the COMM.DRV file in the WINDOWS\SYSTEM directory with another  
driver. Several drivers are available commercially or on BBSs that will solve this problem. A freeware  
driver called CyberCom is available as CYBERC.ZIP on CompuServe in the IBM Communications  
Forum, Library 0. CyberCom will enable Windows communications at speeds up to 115,200 bps if  
you have a 16550 UART installed.  
3.3 Configuring Your Software  
Communications software must be configured to work with your modem, your computer, and the  
remote system it is calling. Fortunately, most communications programs make the process easy by  
providing a default initialization string for your modem as well as defaults for most of the other  
required parameters.  
3.3.1  
Configuring Software for Your Modem  
Because remote computers may have different connection requirements such as speed, number of  
bits, parity, log-on sequences, etc., communications software is typically configured by sessions,  
each session having a unique configuration for a given connection (e.g., to a BBS or commercial on-  
line service). Most communications programs, however, have a separate modem configuration menu  
because modem configurations rarely change from session to session.  
The most important configuration is the modem initialization string. This is a sequence of commands  
the software uses to configure the modem when the communications software is loaded or when a  
session begins. Always begin the initialization string with the ATtention command AT, then follow it  
with the modem reset command, &F. Issuing a reset command before other commands ensures that  
you are starting with a known state.  
The rest of the commands in the initialization string depend on the capabilities of the modem and  
what you want it to do. Some older communications programs require you to create the initialization  
string by yourself. Most modern communications programs, however, provide you with a ready-made  
initialization string that is automatically selected when you choose your modem model from a list. It is  
a poor idea to use an initialization string intended for another modem, especially one from another  
manufacturer, because modem capabilities and command implementations vary from modem to  
modem. However, if your MultiModem does not appear on a modem list, you may use the  
MultiModemII initialization string.  
29  
 
MultiModemBL User Guide  
3.4 PC Initialization Strings  
We recommend the following initialization string for a MultiModem connected to a PC-compatible  
computer when sharing a line with a telephone:  
AT &F X4 S0=0 ^M  
This string resets the modem to the factory default settings, selects extended result codes with NO  
DIAL TONE and BUSY, and turns off auto-answer. ^M must end every string sent to the modem from  
software. It is the ASCII code for the RETURN key on most keyboards, and the default code for the  
carriage return character in the modem and most communications programs. The carriage return  
character is defined in the modem in S-register S3; if you change it, you must also change the  
carriage return character code used in your communications software. If you send a command  
directly to the modem in terminal mode rather than indirectly through communications software, you  
must end the command string by pressing the RETURN key (<CR>) instead of adding ^M to the  
string.  
The following initialization string is for a MultiModem on a telephone line that functions solely as a  
DATA LINE:  
AT &F X4 S0= 2 ^M  
3.4.1  
Changing Default Parameters  
By default, the modem will answer after the first ring and try to communicate with a modem on the  
other end of the line. If you have one telephone line for voice, fax, and modem communications, the  
modem may attempt to answer all incoming calls, voice as well as data. To change auto-answer to  
default off, open your communications program and type the following string in the terminal window:  
AT &F S0=0 &F9 &W0 <CR>  
This string selects the factory default parameters, then turns auto-answer off and stores that setting,  
along with all other current parameters, in nonvolatile memory. The &F9 command causes the  
modem to load the values from nonvolatile memory the next time it receives the &F command. You  
will use the same initialization string as before:  
AT &F X4 ^M  
But now the modem will load the values stored in nonvolatile memory when you turn on the modem  
and when you issue the ATZ or AT&F reset commands.  
Note: Because it clears the command buffer, you should not use ATZ in an initialization string.  
3.4.2  
Other Parameters  
The default values for the other parameters in modem configuration menus rarely need changing.  
They typically include the dialing prefix (ATDT for touch-tone service and ATDP for rotary service),  
the dialing suffix (^M), the hang-up string (+++ATH0^M), and response messages (RING, NO  
CARRIER, BUSY, etc.). Communications software with a host mode might also include an auto-  
answer string (AT S0=1^M).  
30  
 
Chapter 3 - Software Configuration  
3.5 Macintosh Initialization  
Macintosh computers cannot use RTS/CTS hardware flow control without a serial cable wired for  
hardware control. The Macintosh 128 and 512 models cannot use RTS/CTS flow control at all. For  
those Macintoshes turn off the default RTS/CTS hardware flow control, turn on XON/XOFF flow  
control and pacing, and ignore DTR:  
AT &F X4 &E5 &E13 &D0 ^M  
For hardware flow control, use the following initialization string:  
AT &F X4 &E13 &D0 ^M  
Add S0=0 to both strings to disable auto-answer if the modem is on a voice line.  
You can store the initialization string in nonvolatile memory. With your communications software open  
and connected to the modem’s COM port, type the initialization string in the terminal window,  
substituting a carriage return for ^M. To store the string, enter  
AT &F9 &W0 <CR>  
Now you can initialize your modem with the following simple string:  
AT Z ^M  
3.6 Configuring Software for Your Computer  
You must configure your communications software to match your computer’s configuration. If the  
modem is connected to the COM2 serial port, you must tell the software you are using COM2.  
Another important parameter is the serial port baud rate. This is the speed at which your modem  
communicates with your computer, not the speed at which your modem communicates with another  
modem. When V.42bis data compression is enabled, you must have a serial port baud rate four  
times the transmission speed of the modem to fully optimize compression. So if your UART is fast  
enough, you should set the serial port baud rate to a minimum of four times the top speed of your  
modem.  
If you have an 8250 UART, your most reliable serial port speed will be 9600 bps; if you have an  
8250A or a 16450 UART, try 19,200 bps; if you have a 16550 UART or equivalent, a serial port  
setting of 115,200 bps can be set reliably.  
3.6.1  
Configuring Software for the Remote System  
You must meet the requirements of the remote system for successful communications. Though the  
modem can automatically match the speed of the other modem, you must specify parameters such  
as type of flow control, break length, number of data bits, number of stop bits, and parity. If you set  
these parameters incorrectly with the remote system, gibberish will appear on your screen.  
3.6.2  
Terminal Emulation  
If you are accessing the remote computer as if from an on-site terminal, the keyboard codes used by  
your computer may not match the ones used by the remote computer. To be compatible with the  
remote computer, your software must be able to substitute the appropriate codes in what is known as  
terminal emulation. Most communications programs can emulate the most common mainframe  
terminals, including the DEC VT100, VT102, and VT52 terminals, and the basic TTY mode. If in  
doubt about which to choose for a BBS, try ANSI or VT100 first.  
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MultiModemBL User Guide  
3.6.3  
File Transfer Protocols  
When you upload or download files with your modem, the host computer will ask which file transfer  
protocol you want to use. Most communications programs allow you to choose a default protocol.  
Your software’s documentation should list the ones it can use (not all communications programs  
support all protocols). Zmodem is the recommended protocol for most transfers.  
3.7 When to Disable Data Compression  
If your serial port cannot keep up because it has an older UART, you may lose data when using data  
compression. Also, the speed advantage hardware compression gives you is entirely dependent on  
how much the data being transmitted can be compressed. If the data is already in compressed  
form—a .ZIP or a .SIT file, for example—trying to compress it more will actually slow the transmission  
slightly compared to transmitting the same file with compression disabled. This effect will be most  
noticeable if your modem negotiates MNP 5 compression with the other modem. V.42bis will not try  
to further compress a compressed file, but MNP 5 will.  
The command to disable compression is AT &E14 <CR>. If you have an older UART or if you use  
your modem mostly for downloading long, compressed files from BBSs, you may want to include the  
&E14 command in your initialization string as follows:  
AT &F S0=0 X4 &E14 ^M  
As a general rule, you should try to transmit files in already-compressed form rather than relying on  
V.42bis hardware compression. Because software compression is more efficient than hardware  
compression, you will have a higher throughput with the former. Of course, this efficiency does not  
include the time spent compressing and decompressing .ZIP or .SIT files, but it will save on phone  
bills. And hardware compression will still be there for those occasions when it is inconvenient to  
compress a file with software. Note also that when you download files with compression disabled,  
you can use a slower serial port if you have an older UART.  
3.7.1  
Disabling Error Correction  
By default, the modem is set to auto-reliable mode. In this mode the modem determines during the  
handshake whether the other modem is using V.42 error correction. If it is, the modem then switches  
itself to reliable mode and enables error correction. If it is not, the modem remains in non-error  
correction mode.  
Normally, we recommend that you leave the modem set to auto-reliable mode (&E1). However, you  
may encounter some circumstances in which the modem will work better with error correction turned  
off. For example, it has been reported that on CompuServe error correction will slow file transfers at  
modem speeds of 9600 bps and under. If this is a problem for you, you can turn off error correction  
with the command AT &E0, or you can include the command in your initialization string as follows:  
AT &F S0=0 X4 &E0 ^M  
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Chapter 3 - Software Configuration  
3.8 Modem Basics  
You control your modem by issuing AT commands, setting S-Registers, and setting DIP-Switches.  
You can easily change the settings of your DIP-Switches, as they are located on the right side of  
your modem’s chassis. Right now your modem is set up for the most typical user application, that is,  
as a traditional modem set to make a dial-up call to a remote installation where the call is answered  
automatically; therefore, you shouldn’t need to change the DIP-Switches. (If however, you know that  
your application does not follow this profile, please refer to Chapter 9 for full details on DIP-Switch  
settings.)  
While you may operate your modem manually, it is more likely that you will use your data  
communications software to either:  
enter “terminal” mode, where you can “speak most directly” to the modem by issuing AT  
commands, or to  
launch a datacomm session through a set of modem configurations which you select and then  
associate with a target telephone number. Once you have created, saved, and named this set of  
information according to your connection needs and your datacomm software’s conventions, the  
software then simplifies your dialing because you needn’t re-configure your modem, nor run the  
risk of mistakenly keying-in incorrect information.  
Either way, you need to understand that an AT command is the method by which your modem is  
controlled, and must therefore prefix nearly all commands. AT stands for attention, and alerts the  
modem that a command follows. You may enter these commands with either upper- or lowercase  
characters. Entering AT automatically sets the modem’s serial baud rate to match your computer’s  
and also sets the modem’s parity. It also clears the modem’s command buffer.  
Once you’re in terminal mode, enter AT followed by <CR> to check whether your modem is  
operational. If everything’s fine, your modem will respond OK. (Note: refer to Chapter 4 for additional  
details on Dialing, Automatic Answering, Dial Back-Up and Automatic Leased Line Restoral.)  
3.8.1  
Simple Operations  
You can dial a number by using the ATD command and the phone number of the modem with which  
you wish to connect, e.g., ATD6127853500. Your modem will dial the number, and hear a  
“scrambling” noise as the modem negotiates the kind of connection it can make, and once the  
modems have settled on a common connection, you will receive a connect message on your  
computer’s video display. As the modem dials and connects, you may notice changes across its front  
LED panel: the OH (Off Hook) LED lights to let you know the modem is operating as if you had  
picked up the handset to a phone. The CD (Carrier Detect) LED lights to let you know the modem  
has detected a device it can connect to. A speed LED lights to let you know at which speed the  
connection has been made.  
To hang up a call, enter +++ATH<CR>. Your modem will return on hook, just as if you had returned a  
phone’s handset to its cradle. Notice also that the OH, CD and speed LED’s are no longer lit. Your  
video now displays OK, signifying that your modem is ready for your next command.  
3.9 The Answer/Originate - Voice/Data Toggle Switch  
Located on the front of the modem is a Voice/Data "toggle" switch with Originate/Answer capabilities.  
This switch enables the modem to automatically dial a phone number stored in the N1 location of  
memory whenever this switch is toggled. (Note that you must first enter AT$VD1&W0<CR>. This  
command string enables Voice/Data dialing when the Voice/Data toggle switch is activated.)  
If you are "Manually" dialing with an attached telephone device (and not with your keyboard), your  
modem originates when toggled in that position (DOWN); and if you are "Manually" answering  
(modem is not configured to automatically answer via S-Register S0 setup), the modem answers an  
incoming call when toggled in that position (UP).  
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MultiModemBL User Guide  
34  
 
Chapter 4 - Manual Dial and Automatic Answer  
 
MultiModemBL User Guide  
4.1 Introduction  
We’ll assume that yours is the very common application, where you are using a modem to dial up a  
remote computer. The modem has been factory preset for originating a call to a compatible 33,600  
bps modem (also set up for hardware flow control, V.42 error correction, V.42bis data compression  
and CTS/RTS operation). If the answering modem is not set up similarly, the modem automatically  
adjusts to the appropriate protocol.  
4.2 Dialing/On-Line/Answering  
There are several basic steps for “originating” and “answering” in data communication mode:  
1. Load communication software  
2. Dial  
3. Establish On-Line connection  
4. Terminate Call  
A simple way to dial is from the keyboard of your computer or terminal. You enter a command on the  
keyboard to tell the modem to dial.  
If you use a sophisticated communications software package, the software tells you to enter phone  
numbers and other information. If this is the case, the software, and not you, gives the dialing  
commands to the modem. All of the commands, option registers and intelligent features of the  
modem is taken care of by the software.  
If you are giving commands directly to your modem (and not through your software), each command  
must begin with AT (ATtention Characters). AT characters may be entered in upper or lower case.  
Entering AT automatically sets the modem’s speed to match the speed of the computer or terminal,  
and also sets the modem’s parity.  
The AT characters alert the modem that a command follows. The AT Command can also be used to  
clear the command buffer, by simply typing AT and hitting RETURN.  
The letter D in a command causes the modem to dial the numbers immediately following it (e.g.,  
ATD6127853500). You have a choice of either pulse (ATDP) or tone (ATDT) dialing methods.  
The modem responds with “CONNECT” on your video display after the number is dialed and a  
connection signal is detected. The modem is now in “On-Line” mode, and is ready to communicate  
with a host site.  
If no connection signal is detected within 45 seconds (this time period can be adjusted by S-Register  
S7), the modem goes On Hook/hangs up and returns to Command mode. At this point, your video  
displays “NO CARRIER”.  
Enter +++ATH to Hang Up On-Line (bring modem on-hook), and terminate the modem's On-Line  
mode. At this point, your video displays “OK”.  
In addition to the call originating capabilities, the modem can also automatically answer incoming  
calls. You need not be present. You can, however, control the situation by configuring the modem to  
either answer or not to answer, or to answer after a specified number of rings. This is done by setting  
the value of S-Register S0 (modem defaults to automatically answer an incoming call after one ring).  
Refer to Chapter 6 for S-Register details.  
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Chapter 4 - Manual Dial and Automatic Answer  
4.3 Automatic Leased Line Restoral Operation  
When the modem is in Dial Backup mode, it periodically checks the leased line to see if it's  
operational and tries to restore the leased line if possible. S-Register S18 determines how often  
restoral attempts occur. The default for S18 is 30 minutes, and can be set in one minute increments  
from 10 to 255 minutes. Setting the restoral attempts under 10 minutes causes excessive breaks in  
the dial-up operation.  
Note: both local and remote modems must have S-Register S18 set identically. Refer to Chapter 6  
for more information on S-Register S18.  
4.4 Manual Dial Backup Call Termination  
With your modem in leased line mode (DIP-Switch #10 in the DOWN position) and with dial backup  
operation in process, there are two ways to manually terminate the dial backup call (other than  
automatic leased line restoral). In each case, you will try to establish the leased line connection  
because it is back in operating condition. The methods of dial backup call termination are:  
1) Manual Control. The "Voice/Data" switch can be used to change from a dial back line to leased  
line by toggling down once. When that is done, the modem tries the leased line connection, and,  
if it is good, the modem disconnects the dial back call and establishes a leased line connection.  
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50 milliseconds or more, a  
disconnect occurs. This is probably the most common method used by computer systems at the  
automatic answer end of the line to cause the answering modem to disconnect after toggling off  
procedures.  
4.5 Dial Backup and Leased Line Restoral  
The dialing associated with the MultiModem, when in leased line with dial-back mode, involves  
placing a call from the originating modem due to a leased line failure.  
After a preset period of time (determined by S-Register S18), the modem automatically tries to  
restore the leased line.  
The parameters used to determine if a leased line is down (so automatic dial back can occur), is  
based on the modem doing a “retrain” on the leased line due to an error condition in the transmission.  
An error condition is defined as a "hit" on the line (the Carrier gets interrupted).  
The retrain is a "handshake" procedure between the modems to establish the Carrier again. If the  
retrain fails, both modems (originate and answer modems) start their Dial-back timers. The time is  
determined by S-Register S19 settings. The S19 default setting is one minute. During that minute, the  
originate modem tries to establish the leased line link. If the leased line is established during that  
time, the timer is cleared and everything is back to normal. If the timer expires, the modems goes to  
dial-back mode.  
The purpose of the timer for the Answer modem is to determine when it accepts a dial-up call. When  
both timers have expired and the leased line has not been established, the dial-back procedure  
starts. The number dialed is the one stored in location N9 of the originate modem's phone number  
memory. In the preparation for proper dial-back operation, enter the proper number in the N9 location  
using the commands detailed in Chapter 5. Keep in mind that the number also can be dialed in  
V.25bis Command mode.  
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MultiModemBL User Guide  
4.6 Dial-Up Operation  
When your modem is used as a dial-up modem (DIP-Switch #10 in the UP position), it can both  
originate and answer calls. To originate calls, you use the automatic dialing capability of the modem's  
Command mode.  
To do this, use the computer or terminal keyboard to enter a few command letters, followed by the  
phone number you wish to dial. If you have a computer with sophisticated communications software,  
you may end up talking back and forth with the software, and the software will take care of talking to  
the modem.  
It is still possible, however, to dial your data calls using a telephone set. There are few reasons why  
you would want to do this, but if you have a need to use the telephone set to dial, we explain how in  
the next section. We will delay our coverage of Command Mode autodialing, and all other Command  
Mode features, until Chapter 5.  
4.7 Manual Call Origination  
You can use the modem to both originate and answer calls. To originate calls in Asynchronous mode,  
you will most likely use the modem's Command mode, and give the modem automatic dialing  
commands (we will delay our discussion of the Command mode until Chapter 5). When using your  
modem in Synchronous mode, the Command mode is disabled, so you must automatically dial your  
calls with a telephone set. To use manual dialing, you first connect an ordinary telephone set (either  
touch tone or rotary dial) to the modem's PHONE Jack, if you have not already done so. Next, set the  
speed selection, (DIP-Switches #13 and #14), to the speed at which you wish to communicate.  
These DIP-Switches are located on the side of the modem. (Refer to Chapter 9 for DIP-Switch  
settings.) Your computer or terminal may be set for up to 115,200 bps (57,600 bps for 1432 models).  
When your telephone set is connected, you can use it to dial the modem you wish to call. Simply dial  
the number, and then listen to the dialed modem's answer tone. When you hear it, press the Voice/  
Data switch on the front of the modem down (to the Originate position). You don't have to hold it  
down. Just "toggle it" (press it once and let it go). Once you press the switch, the tone you hear  
should change to another pitch, or change into a rough-sounding scrambled noise. You then replace  
the telephone handset in its cradle, and your data communications begins.  
Note that the modem may call manually via the keyboard command ATD, or by pressing the Voice/  
Data switch on the modem's front panel downward. To force the modem to automatically answer  
calls, either type ATA, or press the Voice/Data switch on the modem's front panel upward.  
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Chapter 4 - Manual Dial and Automatic Answer  
4.8 Automatic Answering  
The modem can be used as an automatic answering modem. No special modifications or settings are  
required other than making sure that the Auto-Answer select switch is set to Auto-answer enabled  
(DIP-Switch #5 UP).  
The modem, when in its idle state, is set for Originate mode frequencies. An incoming ring signal  
automatically switches the modem into Answer mode.  
You can program the modem to answer a call after a certain number of rings using S-Register S0  
(see Chapter 6). Refer to Section 4.10 for the handshaking procedures used by the modem when in  
automatic answer mode.  
In many originate-only applications, you may wish to disable the automatic answer capability of the  
modem. If a telephone set is connected to the modem, you may wish to receive incoming calls in a  
voice mode for normal voice conversation. If auto-answer is not disabled, all incoming calls are  
answered by the modem, preventing voice communications. To disable automatic answer, place DIP-  
Switch #5 to the DOWN (Disable Auto Answer) position (refer to Chapter 9).  
Another way to disable automatic answer is to use S-Register S0 to configure the modem to answer  
on the nth ring, where n equals zero (0). Another alternative is to have the modem answer after five  
or six rings, which gives you time to answer it manually if you wish. (See Chapter 6 for S-Register  
information.)  
4.9 Manual Answering  
We have shown that the modem can automatically answer incoming calls. The MultiModem can also  
answer manually, under your control. The most typical application involves you and another person,  
who, after carrying on a voice conversation, want to convert to data communications between your  
modems without having to hang up and dial again.  
The problem here is that both modems are in originate mode. For two modems to communicate, one  
of them must be in originate mode and the other must be in answer mode. The solution here is to  
force either one of the two modems to Answer mode, and the other to Originate mode.  
The modem can be forced into either Answer mode or Originate mode by using the Voice/Data  
switch on the front of the modem.  
In our example, let's say that you and your friend Bill have just had a voice conversation. Both of you  
have your telephones connected to your modems, and your modems are connected to computers or  
terminals. Set the speed switches to the proper speed on both modems. To switch to Data mode  
from Voice mode, you would switch the Voice/Data switch Down (to the Originate position), and Bill  
would switch his up to Answer. This switches your modem to the originate on-line mode, and Bill's to  
the Answer on-line mode. You would both then hang up your telephone handsets, and continue the  
conversation via your keyboards.  
39  
 
MultiModemBL User Guide  
4.10 Handshaking Details  
This section briefly explains what happens between two modems in a normal call. We are assuming  
that there are MultiModems at both the originating and at the answering end of the telephone line. (If  
other brands of modems are used with our modems, they will still communicate, but each  
manufacturer tends to use slightly different delay timings and sequences, and many of the brands  
vary in their LED designations.)  
When a call is dialed from the originating modem, the called modem responds to the ringing by  
switching into Answer mode and by turning on its RI (Ring Indicator, RS-232C/V.24 Pin 22) signal as  
the rings are detected. (The BL-MAC models do not use DTR.)  
Note that in order for the called modem to be able to answer the call, it must have a high DTR (Data  
Terminal Ready) signal. This signal comes from the computer or terminal to which it is attached, on  
RS-232C Pin 20.  
When the called modem answers the call, its OH (Off Hook) circuit comes on and the ringing stops.  
Two seconds after the call is answered, the called modem begins transmitting its answerback tone.  
The originating modem, which has been off hook and waiting for the answerback tone, turns on its  
transmitter when it hears the tone. Then after a one second delay, the orignating modem's CD  
(Carrier Detect) comes on.  
The called modem then responds to the originating modem by turning on its CD (Carrier Detect)  
signal, and the handshaking is completed.  
Note: With the modem in Reliable or Auto-Reliable mode, some additional handshaking takes place.  
This is explained in Section 5.4.8.  
4.11 Call Termination  
There are a number of ways to terminate a call, or simply stated, hang up. They are:  
1) Command Mode Control. To terminate a call by Command Mode, enter +++ATH then  
RETURN; or, send a BREAK signal followed by ATH and a RETURN.  
2) DTR Control. If DTR (Data Terminal Ready) is turned off for 50 milliseconds or more, a  
disconnect occurs. This is probably the most common method used by computer systems at the  
automatic answer end of the line to cause the answering modem to disconnect after logging off  
procedures.  
3) Loss of Carrier. After a data connection is established, the modem disconnects if a loss of  
carrier occurs for 700 milliseconds (0.7 seconds) or more. Note that one cause of carrier loss  
would be if one of the modems disconnect normally.  
4) Abort Timer.  
Answer Mode: When OH (Off Hook) comes on, the called modem starts a forty-five-second  
timer and waits for a carrier signal from the originating modem. If carrier is not detected within  
this period, the modem disconnects (hangs up) and is ready for another call.  
Originate Mode: The abort timer functions the same as in answer mode, except that the timer  
begins after the modem has completed dialing, instead of when it first goes off hook. It is possible  
to change this forty-five second wait period to any other value (from 0 seconds up to 255  
seconds), or to disable the timer completely by re-configuring S-Register S7 (see Chapter 6).  
5) Inactivity Timer. Causes the modem to disconnect if no data is transmitted or received for a  
specified time. The timer is restored any time a character is passed through the serial port in  
either a send or receive state. This timer runs in both normal or reliable connections and is  
controlled by S-Register S30. The Inactivity Timer can be disabled by setting S30 to 0, which is  
the factory default setting.  
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Chapter 5 - Command Mode  
 
MultiModemBL User Guide  
5.1 Introduction  
AT commands are the means by which you, and your communications software, are able to  
communicate with and configure your modem. They enable you to establish, read, and modify  
parameters in addition to dialing. The following provides both a summary and a detailed explanation  
of the AT commands recognized by the MultiModem.  
5.1.1  
AT Command Editing  
The BACKSPACE key on your keyboard can be used to edit characters in the AT command line. An  
AT command is not executed until the RETURN key is pressed. The BACKSPACE key erases the  
previous character for reentering.  
The BACKSPACE key does not erase the AT characters once they are entered. If your keyboard  
has no BACKSPACE key, CTRL-H does the same thing. The character recognized by the modem  
as BACKSPACE may be changed to any other ASCII character with S-Register S5.  
If you wish to cancel an entire command that has been entered but not yet executed, enter CTRL-X.  
This also clears the command buffer. The effect is the same as backspacing to cancel the entire  
command, only quicker.  
Characters entered in a command are stored in the modem's Command Buffer (memory) until  
executed by hitting RETURN. The Command Buffer's capacity is sixty characters. The Attention  
Characters AT do not count in the sixty allowed Command characters. Spaces, which may be used  
for increased display readability, may be used when entering a command, but are not stored in the  
Command Buffer and are not counted in the sixty allowed characters. Hyphens, parentheses, etc. are  
not allowed.  
If the sixty character limit is exceeded or if invalid characters are entered, the Command Buffer  
automatically erases, and an ERROR message appears. You would then re-enter your command  
within the sixty-character maximum, using only the allowed characters.  
42  
 
Chapter 5 - Command Mode  
5.1.2  
Functional Modes  
The MultiModem can be in one of two functional states (see Figure 5-1). These are "Command  
mode" and "On-line mode". (There is also an in-between state, "Wait-for-Carrier", where the modem  
is out of Command mode but not yet really On-Line.  
When the modem is initially powered up, it is in Command mode and is ready to accept commands  
from your keyboard or software. The modem enters On-line mode after dialing, making a connection  
with another modem, and then detecting a valid carrier signal. If no carrier is detected within a certain  
time frame, the modem abandons the call and re-enters Command mode.  
Once on line, the modem exits On-line mode if one of two conditions is met. If the carrier is lost or  
intentionally dropped, the modem hangs up and re-enters Command mode. Also, if the modem  
recognizes the Escape sequence for which it is configured (i.e., either the Escape characters in the  
serial data stream, the Remote Escape characters in the modulated data stream, or the Break  
signal), the modem will exit On-line mode, retain the datacomm link, and enter Command mode.  
You can force the modem into On-line mode without dialing by sending the ATD or ATA command to  
the modem.  
+++AT  
COMMAND  
MODE  
HANG  
UP  
Dial (D or A) command,  
or incoming phone call  
WAIT FOR  
CARRIER  
No carrier  
detected  
Carrier detected  
ON-LINE  
MODE  
AT0 Command  
Carrier lost  
Figure 5-1. Functional Modes  
43  
 
MultiModemBL User Guide  
5.2 Summary of AT Commands  
A wide variety of autodial operations and modem options can be controlled when the modem is in  
Command Mode. Remember, nearly all commands begin with AT.  
These commands are organized into several functional groups. An alphabetical summary of  
commands is provided in Appendix D.  
HOW TO  
COMMANDS  
DIAL  
D Dial  
A: or : Continuous Redial (Not Active in BLK models)  
$D  
$VD  
N
DTR Dialing  
Voice/Data Dialing  
Dial a Stored Number  
MODIFY DIALING  
PROCEDURES  
P/T  
&P  
,
Y
W
;
Pulse/Tone Dialing  
Set Pulse Dial Ratios (Not Active in BLK models)  
Automatic Pauses in dialing  
Long Space Disconnect  
Wait for New Dial Tone  
Return to Command Mode After Dial  
Command  
R
!
Reverse Mode of Operation  
Flash On Hook  
$
@
AT&T "Calling Card" Tones  
Quiet Answer  
MEMORIZE PHONE  
NUMBERS  
D...N Store Phone Numbers  
NN  
L
Number Linking  
List Numbers Stored in Memory  
STORE MODEM  
CONFIGURATIONS  
AND DEFAULTS  
&F  
&W  
Load Factory Defaults  
Store Configuration & S-Register  
Parameters  
Z
Reset Modem  
V
Result Code Terse/Verbose  
UNIX/"Spoofing”  
Synchronous/Asynchronous Mode Select  
Synchronous Transmit Clock Select  
$SP  
&M  
&X  
CONFIGURE  
COMMAND  
RESPONSES  
Q
&Q  
E
Result Codes Enable/Disable Response  
Result Code Selection  
Echo Command Characters  
V
Result Code Terse/Verbose  
X
Result Code...Basic/Extended/Call Progress  
CONDITION  
PHONE LINE  
&G  
M
Guard Tones (Not Active in BLK models)  
Monitor Phone Line  
&T  
#T  
B
Remote Digital Loop Signal  
Enable/Disable Trellis Coded Modulation  
Bell/V.21 Tones (Not Active in BLK models)  
Fallback When On-Line  
#F  
&CD Cleardown at Disconnect (2834 Series only)  
#A Auto-Speed Detect  
44  
 
Chapter 5 - Command Mode  
CONTROL RS232C  
INTERFACE  
&C  
&D  
&R  
&S  
&RF  
&SF  
Carrier Detect Control  
Data Terminal Ready Control  
Clear To Send Control  
Data Set Ready Control  
CTS/RTS Control  
DSR/CD Control  
CONFIGURE  
ERROR  
CORRECTION  
&E0  
&E1  
&E2  
#L0  
#L1  
#L2  
#L3  
$A  
Normal Mode  
Auto-Reliable Mode  
Reliable Mode  
Negotiate V.42 Mode During Handshake  
MNP On/LAPM Off  
LAPM On/MNP Off  
Direct LAPM/Phase Out Handshake  
Auto-Reliable Buffering  
$F  
$R  
Enable/Disable Auto-Reliable Fallback Character  
Retransmit Count  
$E  
Error Correction at 300 bps  
CONFIGURE  
FLOW CONTROL  
&E3  
&E4  
&E5  
&E6  
&E7  
#X  
Flow Control Disabled  
Hardware Flow Control  
Xon/Xoff Modem-Initiated  
Xon/Xoff Modem Responds/No Pass-Through  
Xon/Xoff Modem Responds/Pass-Through Allowed  
Send Single/Multiple Xoff Characters  
Enq/Ack Off  
&E8  
&E9  
Enq/Ack On  
&E10 Normal Mode Modem Flow Control Off  
&E11 Normal Mode Modem Flow Control On  
&E12 Computer-Initiated/Off  
&E13 Computer-Initiated/On  
&BS Maximum Block Size  
$EB  
#P  
10/11 bit Asynchronous Format  
Parity Selection  
CONFIGURE DATA  
COMPRESSION  
&E14 Data Compression Disabled  
&E15 Data Compression Enabled  
CONFIGURE SPEED $BA0 Speed Conversion On  
CONVERSION  
$BA1 Speed Conversion Off  
$MB Set modem speed (e.g.,$MB14400)  
$SB  
Set serial port speed (e.g.,$SB57600)  
EXECUTE  
IMMEDIATE  
ACTION  
$H  
I
Help  
Product Code Inquiry  
I 9  
L5  
L6  
L7  
L8  
H
Windows 95 Autodetect Inquiry (2834 Series only)  
List Current Operating Parameters  
List S-Register Values  
List additional Configuration Parameters  
List On-Line Diagnostics  
Off Hook  
COMMANDS  
+++AT<CR> Escape Sequence: Entering Command Mode while On-Line  
%E  
A
Escape Sequence Options...Entering Command Mode while On-Line  
Force Answer Mode  
O
Exit Command Mode/Go Back On-Line  
45  
 
MultiModemBL User Guide  
EXECUTE  
LINE  
%DF Format Line Probe Display (Graph or Table Format)  
%DP Enable/Disable Reading Line Probe From DSP during handshake  
PROBE  
L9  
Display of Signal Strength Information  
COMMANDS  
(2834 Series only)  
L10  
Display Signal to Noise Ratio (SNR)  
L11 Display of Noise Information  
&RP Initiates Retrain to Read Line Probe Parameters  
READ AND  
ASSIGN  
Sr?  
Sr=  
Read Current S-Register Value  
Assign S-Register Value  
S-REGISTER  
VALUES  
REMOTE  
#CBN Passwords for Callback Phone Numbers  
CONFIGURATION  
& CALLBACK  
#DB  
#I  
Callback Security Enable/Disable  
Change LOGIN Password  
SECURITY  
#RCBNxx  
Erase Password Linked with Memory Location xx  
Change SETUP Password  
#S  
TEST MODEM  
U
Self-Test Modem (Chapter 8)  
&T  
Enable/Disable Digital Loopback Signal  
46  
 
Chapter 5 - Command Mode  
5.3 Result Codes  
The Command mode provides you with several responses, or “Result Codes”, that can aid you in  
Command mode operation. These Result Codes are displayed on your video monitor.  
You can choose result codes that closely match those of the standard AT command set, or choose  
enhanced function result codes that have been used in Multi-Tech modems ("Multi-Tech" responses).  
The &Q command selects which result codes will be used.  
You can choose to have these Result Codes displayed in either “verbose” (full words) or “terse”  
(digits) format. This is controlled by the ATV0 (terse) or ATV1 (verbose) commands. The modem  
defaults to verbose format.  
AT&Q0 selects Multi-Tech responses with Reliable/LAPM/Compression modifiers. The terse  
response code for CONNECT 2400 is 9. AT&Q1 selects Standard AT command set responses. The  
terse result code for CONNECT 2400 is 10.  
The following tables define the result codes generated by the &Q command (refer to Appendix G for  
Result Code Summary).  
"Multi-Tech" Result Codes  
2834 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
1
2
3
4
5*  
6
7
8
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
NO DIALTONE  
BUSY  
11*  
12*  
13*  
19*  
21*  
24*  
26*  
28*  
31*  
33*  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
CONNECT 21600  
CONNECT 24000  
CONNECT 26400  
CONNECT 28800  
CONNECT 31200  
CONNECT 33600  
NO ANSWER  
CONNECT 2400  
9*  
1932 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
1
2
3
4
5*  
7
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
BUSY  
8
9*  
11*  
12*  
13*  
19*  
NO ANSWER  
CONNECT 2400  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
1432 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
OK  
7
BUSY  
1
2
3
4
CONNECT  
RING  
NO CARRIER  
ERROR  
8
9*  
11*  
12*  
13*  
NO ANSWER  
CONNECT 2400  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
5*  
CONNECT 1200  
* With MNP error correction on, RELIABLE (or R) is added to these result codes. With LAP-M error  
correction on, LAP-M (or L) is added to these result codes. With data compression on,  
COMPRESSED (or C) is added. (Note these "Extended" Result Codes are displayed when your  
modem is set up to do so with an X1, X2, X3, or X4 command.)  
47  
 
MultiModemBL User Guide  
"Standard AT" Result Codes  
2834 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
1
2
3
4
5
6
7
8
9
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
NO DIALTONE  
BUSY  
11  
12  
13  
19  
21  
24  
26  
28  
31  
33  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
CONNECT 21600  
CONNECT 24000  
CONNECT 26400  
CONNECT 28800  
CONNECT 31200  
CONNECT 33600  
NO ANSWER  
CONNECT 2400  
1932 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
1
2
3
4
5
7
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
BUSY  
8
9
11  
12  
13  
19  
NO ANSWER  
CONNECT 2400  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
1432 Series  
TERSE  
VERBOSE  
TERSE  
VERBOSE  
0
1
2
3
4
5
OK  
CONNECT  
RING  
NO CARRIER  
ERROR  
CONNECT 1200  
7
8
9
11  
12  
13  
BUSY  
NO ANSWER  
CONNECT 2400  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
*Reliable/Compression modifiers are not displayed with Standard AT Result Codes.  
48  
 
Chapter 5 - Command Mode  
5.4 Dialing Commands  
5.4.1  
Dialing Action Commands  
Dial Command D  
The letter D in a command causes the modem to dial the telephone number immediately following it.  
For example, if you enter ATD5551212 and hit RETURN, the modem dials the number 555-1212.  
The D command is also used in conjunction with a telephone set for manual dialing. You dial the  
number on your telephone set, and after hearing the answer tone on your handset, you type ATD on  
your keyboard and hit RETURN. Then hang up the headset. Unless you have a specific need to dial  
in this manner, we recommend you use the first method, where the telephone number is entered on  
your keyboard.  
The modem gives you several choices of dialing methods. You can use tone or pulse dialing, by  
inserting a letter T or a P in the command string. (See Section 5.4.2 on Dial Modifiers).  
You can also configure the modem to either wait for and detect dial tones and busy signals (which we  
call “Wait-for-Dial-Tone” dialing or “Smart” dialing), or work with timed pauses without dial tone and  
busy signal detection (which we call “Blind” dialing; see Section on “X” Command.)  
Note: There is another method of dialing, called “DTR Dialing”, where by manipulating the DTR  
signal on pin 20 of the RS-232C/V.24 interface, a number stored in the modem's memory is  
automatically dialed. See description of $D command (in this section) for details.  
Continuous Redial (not used in BLI/BLK) A: or :  
If you select the Wait-For-Dial-Tone method of dialing (see X3 or X4 command), you can command  
the modem to continuously redial (up to 10 re-dials for DOC units) a busy number until your call is  
answered. This is done with the A: command.  
This command would be used only if you had already reached a busy number after executing a  
normal dial command. You simply enter A: (you need not enter AT, nor do you need to hit RETURN),  
and the modem will redial the number for you. If you again reach a busy signal, it re-dials again and  
again until it no longer detects a busy signal. You can stop the modem from re-dialing by pressing  
any key.  
Another method used to cause the modem to redial a phone number continuously is to enter a colon  
: at the end of the phone number. The result is the same as if you had entered A: after personally  
observing that the number was busy on the first dialing attempt. Using the colon in the dialing string is  
a step saver.  
Dialing a Stored Number N  
A telephone number that you have stored in the modem’s number memory may be automatically  
dialed by entering ATNn where n = 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. For example, a number stored at N3  
would be dialed by entering ATN3 and RETURN. Do not include the letter D in this command, or the  
stored number will be erased (also see Section 5.4.3., on Phone Number Memory Commands).  
DTR Dialing $D  
An alternate method of causing the modem to automatically dial is DTR Dialing. Data Terminal Ready  
(DTR) is a signal that comes into the modem from the terminal or computer to which it is connected,  
on pin 20 of the RS-232C interface. In DTR dialing, the modem automatically dials a stored number  
as soon as it receives a high DTR Signal. The DTR dialing method is popular in synchronous  
applications.  
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MultiModemBL User Guide  
To activate DTR Dialing, enter AT$D1 and hit RETURN. The modem dials the phone number stored  
in the N0 location of memory when it receives a high DTR signal. DTR must remain high for the  
duration of the call, until disconnect. To deactivate DTR dialing, enter AT$D0 and hit RETURN.  
Note when using DTR Dialing in a synchronous application, be sure DIP-Switch #8 is in the UP  
position to disable V.25bis Command mode.  
Voice/Data Dialing $VD  
Another alternate method of causing the modem to automatically dial is Voice/Data Dialing. With  
Voice/Data Dialing, the modem automatically dials the phone number stored in the N1 position of  
memory whenever the Voice/Data switch is toggled. You must first enter AT$VD1&W0<CR>. This  
command string enables Voice/Data dialing when the Voice/Data toggle switch is activated. To  
disable Voice/Data Dialing (default), enter the command AT$VD0 W0<CR>.  
5.4.2  
Dial Modifier Commands  
There are several command characters that can be included within a dialing command (following the  
letter D), called “Dial Modifiers”. They have various functions, including the selection of Pulse or Tone  
Dialing, pauses in the dial sequence, automatic re-dials if a number is busy, and reverting to the  
Command mode or switching to the Answer mode after dialing.  
Pulse or Tone Dial P T  
The modem dials numbers using either pulse or tone dialing, or a combination of both methods.  
Pulse dialing is a method used by rotary-dial telephones, which involves the timed opening and  
closing of line relay.  
Tone dialing is the method used by push-button (touch tone) telephones, and is sometimes referred  
to as DTMF, or Dual-Tone Multi-Frequency dialing.  
The method used is selected by including a P for Pulse or a T for Tone in the dialing command, right  
before the digits you wish to have dialed in that manner.  
For example, you would pulse-dial the number 555-1212 by entering ATDP5551212 and hitting  
RETURN. You could tone-dial the same number by entering ATDT5551212 and hitting RETURN. If  
neither Pulse nor Tone dialing is specified in the dial command, the modem uses whatever method  
used last. If the modem has been reset or just powered up, it uses Pulse dialing, even if the letter P is  
not included in your dial command.  
Nearly all telephone systems in the U.S. are now compatible with tone dialing. Since that is the faster  
method, you will probably choose the tone method for your dialing.  
An example of combining pulse and tone dialing could involve a PBX system where 9 had to be  
pulse-dialed first, then the rest of the number tone-dialed after pausing for a second dial tone. The  
number would be dialed by entering ATDP9, T5551212 and RETURN. (The comma causes a pause,  
which we’ll explain soon.)  
Set Pulse Dial Ratios &P (Not used in BLK)  
This command sets the time ratios between the open and closed portions of the dialing pulse  
frequencies. To set the dialing pulse ratio of 60 mSec to 40 mSec, enter AT&P0. To set a ratio of 67  
mSec to 33 mSec, enter AT&P1. The factory default is &P0.  
50  
 
Chapter 5 - Command Mode  
Automatic Pauses in Dialing ,  
You can cause the modem to pause during the dialing sequence by entering a comma character  
where the pause is desired. This pause lasts two seconds. If a longer pause is desired, more than  
one comma may be entered consecutively, with each comma causing a two second pause. You also  
have the option of changing the length of the pause caused by the comma, from two seconds to any  
other value from 0 up to 255 seconds. This is done by setting S-Register S8 (refer to Chapter 6).  
Each comma in a dialing command counts as one of the sixty allowed characters.  
Long Space Disconnect Y  
When two modems are connected in Normal mode (i.e. without error correction) there is no "polite"  
means of requesting a disconnect. A link disconnect request packet is sent under reliable  
connections. As a result some "garbage" may be received when a hang-up command is issued. The  
Y1 command enables the modem to use the break signal which accomplishes the hang-up as an  
instruction to shut off its receiver and disconnect (both modems must have Y1 enabled for this  
feature to be effective). Y0 (factory default) disables this function.  
Wait for New Dial-Tone W  
A W inserted in the dialing command causes the modem to wait for another dial tone, and not resume  
dialing until another dial tone is detected.  
It is not necessary to enter a W at the beginning of the dialing command to wait for a modem dial  
tone, because the modem will do that first (pause automatically).  
In order for this command to work, you must select Wait-For-Dial Tone dialing with the X2 or X4  
command, so that your modem will be able to detect the dial tone.  
Return to Command Mode After Dial Command Execution ;  
A semicolon (;), entered as the last character of a dialing command causes the modem to return to  
the Command mode immediately after executing the command, instead of waiting for a carrier signal  
and going on line.  
For example, entering ATDT5551212; would tone-dial the number, and do nothing afterwards except  
go back into Command mode. This can be useful in dialing applications where modem data transfer  
is not desired, such as voice communications, or in applications involving the use of touch tones as a  
data entry method, such as bank-by-phone.  
Reverse the Mode of Operation R  
In certain operations you may need to reverse the mode of operation for your modem from originate  
to answer or answer to originate so that it would answer the phone and go into answer mode. This  
command turns off the reversing function with the R0 command and turns it on with the R1 command  
with the modem in either command mode. If you want to reverse from the originate mode, use R (with  
no number) in the dialing string.  
Flash On Hook !  
Some switchboard systems react to a momentary On Hook. An exclamation mark inserted in the  
command causes the modem to “flash” on hook for a half of a second (90 mSec in BLK), as if you  
had held the switch hook button on a telephone down for a half second.  
For example, to flash On Hook after dialing the number 555-1234 in order to transfer to Extension  
#5678, you might enter ATDT5551234,,!5678. The commas cause a 4 second pause (just to be  
safe).  
51  
 
MultiModemBL User Guide  
"Calling Card" Detect Tones $  
The modem has the capability to detect AT&T "calling card" tones for the purpose of utilizing the  
user's calling card number to originate an on-line connection. An $ symbol placed in the dialing string  
causes the modem to pause and wait for an AT&T "calling card" or a 1600 Hz tone (prevalent in the  
United Kingdom). When the tone is detected, the rest of the dialing string is processed. If no tones  
are detected within the time period set by S-Register S7 (default 45 seconds), the modem will abort  
by indicating a NO CARRIER message. Hitting any key also aborts the $ command.  
The following is an example of this command:  
ATDT1028806127853500$123456789  
(access/phone number) (credit card number)  
Quiet Answer @  
The @ command causes the modem to wait before processing the next symbol in the dialing string.  
The wait is for one or more ringbacks followed by 5 seconds of silence. If the time specified by S-  
Register S7 passes before the rings and silence, a NO ANSWER (R) result code is processed. The  
@ command is used for accessing a system that does not provide a dial tone.  
For example, ATDT5551212@6313550 causes the modem to dial the first number (555-1212) and  
wait for the time specified in S7 for at least one ringback and 5 seconds of silence. If a busy signal is  
detected, the modem hangs up and generates a BUSY result code. If it does not detect 5 seconds of  
silence, a NO ANSWER result code is generated after hanging up. If 5 seconds of silence is  
detected, the second number (631-3550) is then dialed.  
52  
 
Chapter 5 - Command Mode  
5.4.3  
Phone Number Memory Commands  
Storing Phone Numbers D...N  
A telephone number and command line of up to sixty characters may be stored in the modem’s  
number memory. As many as ten of these numbers may be stored. Each number will be given a  
name, using the codes N0, N1, N2 up to N9.  
A phone number is stored by entering ATD, then the number as it would be dialed, along with any P,  
T, R, ; or comma characters, and then entering N followed by the number’s “name,” which would be  
any number from 0 through 9, and then hitting RETURN.  
For example, the tone-dialed number 1-612-631-3550 would be stored as number N3 by entering  
ATDT16126313550N3 and RETURN. The number is not dialed with this store command. After  
storing a number, check to see that it has been stored correctly by typing ATL and hitting RETURN.  
When phone numbers are stored, the entire command line is also stored so that you can effectively  
create a macro for each number. For example, if you know a particular number needs to have  
extended result codes, detect busy or dial tone, error correction, Xon/Xoff flow control, pacing, and  
data compression enabled, the command line would be:  
ATX4&E1&E5&E13&E15DT16126313550N3. This would store the entire command at location N3.  
Number Linking NN  
You may command the modem to dial another number automatically if the first number dialed is  
busy. This would be useful in a situation where a computer can be accessed through more than one  
phone number. This is called “linking”.  
To link the number in N1 to the number N2, simply enter ATN1N2 and hit RETURN. Several numbers  
can be linked in the same command. For example, you could link N1 to N2 to N3 to N4 by entering  
ATN1N2N3N4 and RETURN or you could link N1 to N2 and back to N1 and then back to N2 by  
entering ATN1N2N1N2 and RETURN.  
The only limit on the number of numbers that can be linked is the 60 characters allowed in a  
command line. Number linking can not be used with blind dialing, since busy signals would not be  
detected. You would have to select the Wait-for-Dial tone dialing method using the X Command in  
order to use the Number Linking feature.  
Listing Numbers Stored in Memory L  
Telephone numbers that you have stored in the modem’s memory may be listed and displayed with  
the L command. It will display all ten stored N numbers in a format like that shown below. All digits  
and command letters will be shown. The number’s “name” (0 thru 9) is shown first, followed by the  
complete dialing command and telephone number as originally entered.  
Simply enter ATL and hit RETURN to display these numbers on your video screen or printer. An  
example of an L command listing is shown below:  
0
1
2
3
4
5
6
7
8
9
DT14082345678  
DT16125551212;  
DP9,T14089876543  
DT3738315,12101,16126313550  
DT6313551R  
DP9,4258513  
DTX4&E1&E5&E13&E15DT16126313550  
DT12138880123  
53  
 
MultiModemBL User Guide  
5.4.4  
Configuration and Default Storage Commands  
Store Configuration & S-Register Parameters in Non-Volatile Memory &W  
The modem can store configuration parameters and S-Register values in its nonvolatile read/write  
Random Access Memory (RAM) memory. The &W command does this, which prevents any re-  
configuration from being lost on a power-down or Reset (ATZ) condition.  
&W0 (or AT&W) causes the modem to store your customized AT command settings and S-Register  
values in its nonvolatile RAM. &W0 also sets the modem so that it reads your customized settings  
stored in nonvolatile RAM when powered down or reset. (The &W0 command only changes the  
settings stored in nonvolatile RAM that you specifically intend to alter. All other default parameters  
are applicable.)  
&W1 causes the modem not to store your customized settings to nonvolatile RAM so that, after  
powering down or resetting the modem, it reads the factory default settings stored in ROM.  
Loading Factory Defaults &F  
The &F command provides a choice between customized configuration settings in RAM and the  
factory default configuration settings in ROM. The &F8 and &F9 commands define the function of the  
&F command.  
The modem is shipped from the factory with a pre-configured set of command and S-Register default  
settings. This set of factory defaults can be recalled by issuing the &F command.  
In addition to being able to recall the factory-installed defaults, the &F command can also recall those  
defaults stored under &W0.  
This is done using the &F9 command. If you have stored parameters with the &W0 command and  
wish these settings to always be used as your defaults, you would enter &F9&W0.  
To return the &F command to read factory installed defaults, enter &F8&W0. &F8 is the factory  
default.  
Many datacomm program issue the &F command automatically- the &F9 command allows the user  
to select their own factory defaults. Note that the &F8/&F9 commands should be used with &W0.  
Following is a summary of how the &F and Z reset commands interact with the &W command; note  
how the &F reset command operates differently from the Z reset command:  
Previous Command AT&F  
Power-On and ATZ  
AT&W1 (default)  
AT&W0  
AT&F8&W0  
AT&F9&W0  
ROM  
ROM  
ROM  
NVRAM  
ROM  
NVRAM  
NVRAM  
NVRAM  
Modem Reset Z  
The Z command can be used to reset the entire Command Mode buffer and the result is the same as  
if you had disconnected, and then reconnected power to the modem. When an ATZ command is  
executed, the state of the &W command determines where the default values originate. &W0 defaults  
come from RAM and &W1 defaults come from ROM.  
54  
 
Chapter 5 - Command Mode  
Unix UUCP Spoofing $SP  
The modem can be configured in a Unix environment that employs ACK flow control as a means of  
monitoring data integrity. The modem can do “UUCP spoofing”, where the modem is able to generate  
ACKs at the DTE interface. Data is transmitted more time efficiently because the delay of waiting for  
data to be received, then for an ACK to be returned at the remote end, is eliminated. The $SP1  
command enables UUCP spoofing and the default command $SP0 disables UUCP spoofing.  
Async/Sync Mode Switching &M  
This command can be used to set the on-line mode to either synchronous or asynchronous. AT&M0  
will set the modem to Asynchronous mode, and all communications will be Asynchronous, in both  
On-line and Command modes. AT&M1 causes the modem to communicate asynchronously when in  
Command mode and switch to synchronous mode while on-line. The modem defaults to &M0  
(asynchronous communications) on reset or power-up.  
Synchronous Transmit Clock Select &X  
The &X command selects the Synchronous Transmit Clock Source in conjunction with DIP-Switch  
#11. DIP-Switch #11 in the UP position enables External clocking. DIP-Switch #11 in the DOWN  
position enables Internal clocking (default position). External clocking is when the DTE provides  
transmit clocking to the modem on pin 24 of the RS-232C interface.  
&X0 is the default setting, which allows DIP-Switch #11 to control Internal/External Clocking (default  
Internal). Internal clocking is when the modem provides transmit clock to the DTE on pin 15 of the  
RS-232C/V.24 interface. The &X1 command overrides DIP-Switch #11 and selects External clocking.  
If DIP-Switch #11 is UP (External clocking), you can not override Internal clocking. &X2 enables  
Slave Clocking. The &X2 Command causes the modem to generate the transmit clock timing (pin 15)  
from the receive clock (pin 17) from the DTE (therefore 15 and 17 are the same). In this mode (Slave  
Clocking), all timing is controlled by the receive clock.  
55  
 
MultiModemBL User Guide  
5.4.5  
Command Response (Result Code) Commands  
Echo Command Mode Characters E  
If the modem is connected to a full-duplex computer, it may be necessary for the modem to be  
configured to echo back characters entered while in the Command Mode in order for them to be  
displayed. The E command is used to configure the Command Mode echo, with ATE0 disabling the  
echo and ATE1 enabling the echo (default).  
Result Codes Enable/Disable and No Response Answer Q  
The Q command enables or disables Result Codes and the No Response Answer mode of operation.  
Result Codes may be disabled altogether in certain applications, such as computer-controlled auto  
dialing, using the Q command. ATQ1 disables Result Code transmissions. ATQ0 (or ATQ) enables  
Result Code transmission.  
Regarding No Response Answer, you may want the answer mode handled without responses and  
echo turned off, but want the originate mode still intelligent. This is called the No Response Answer  
mode. ATQ2 selects the No Response Answer mode. If you do not select any mode, the factory  
default setting (enable Result Codes) is automatically selected.  
Result Codes ("Multi-Tech" or "Standard AT") &Q  
The modem gives you a choice between the Multi-Tech Result Codes, and Result Codes that more  
closely match the standard AT command set responses (see Section 5.3).  
AT&Q1 selects AT responses with no Reliable/Compression modifiers. With this command, the  
terse result code for CONNECT 2400 is 10.  
AT&Q0 selects Multi-Tech responses with Reliable/Compression modifiers. With this command, the  
terse result code for CONNECT 2400 is 9.  
Result Codes (Verbose/Terse) V  
The V command controls whether the modem’s result codes are displayed as word (“verbose”) or  
single digit (“terse”) messages.  
For example, if after dialing, no carrier signal is detected, the resulting message can be displayed  
either as NO CARRIER, or as the digit 3.  
Entering ATV0 (or ATV) causes the modem to display the Result Codes as digits, while ATV1  
displays them as words. If you do not select a method, the factory default setting causes the modem  
to display Result Codes as words.  
56  
 
Chapter 5 - Command Mode  
Result Codes (Basic and Extended) and Call Progress Selection X  
The X Command is used to select one of two possible dialing methods (“dumb” or “smart”), and to  
select various response combinations related to these methods. You can choose to have certain  
responses suppressed, or whether or not you want speed indications along with the CONNECT  
responses. You can also pick and choose certain responses in order to match up with “Standard AT”  
responses. (Refer to Appendix G for a summary of Result Codes.)  
The modem provides “Basic” and “Extended” Result Code sets. The difference between the two is  
the Basic set provides one response (CONNECT) to indicate a connection, while the Extended set  
provides several responses for different speeds (CONNECT, CONNECT 2400, CONNECT 4800,  
CONNECT 9600, Etc.).  
When the Extended set is chosen, you also have the option of matching them up with Standard AT  
2400 response code sets, by including or not including the BUSY and/or NO DIAL TONE  
responses while excluding the DIAL TONE response. The X command is used to select which  
responses are provided.  
Regarding the modem’s method of dialing, the modem can detect standard dial tones and busy  
signals. This capability (“smart dialing”) allows the modem to wait for a dial tone, and when one is  
detected, to begin dialing immediately.  
The modem also can detect a distant busy signal, if after dialing, it reaches a busy number. This is  
useful because it allows the modem to immediately abandon a call, rather than wait 45 seconds for a  
carrier signal that will never come. S-Register S7 defines the wait for carrier time (refer to Chapter 6).  
The modem gives you a choice between the wait-for-dial-tone (“smart”) method we just described,  
and blind (“dumb”) dialing, where instead of detecting actual dial tones, the modem relies on timed  
pauses. When the wait-for-dial-tone method is chosen, the busy signal detection capability is also  
activated. The X command is also used to select which dialing method is used.  
Five different X commands are available (X0 through X4), with five different effects on the modem’s  
Result Codes.  
X0 Provides the basic (short) result codes and provides “dumb” dial capabilities.  
X1 Provides the extended result codes and provides “dumb” dial capabilities.  
The remaining X commands affect Call Progress, and turn on Extended Result Codes.  
X2 Looks for dial tone only and will not provide a busy response.  
X3 Looks for busy only and not look for dial tone.  
X4 Looks for dial tone and for busy.  
The factory default setting is X0, which selects Basic Result Codes and the blind (“dumb”) method of  
dialing.  
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MultiModemBL User Guide  
5.4.6  
Phone Line Conditioning Commands  
Guard Tones (Not Used in BLI or BLK Models) &G  
The &G command is used to control the presence or absence of guard tones from the transmitter  
when in Answer mode, at either 1200 or 2400 bps. Guard tones are used in Europe and other areas  
for the modem to function in the telephone systems. Guard tones are not used in the United States.  
&G0 (default), turns off CCITT guard tones. &G1 turns on 550 Hz guard tones. &G2 turns on 1800  
Hz guard tones. This command is not used in international models.  
Bell/V.21 Tone (Not Used in BLK Models) B  
The B command selects the frequency that the modem uses for its answer tone. (The answer tone is  
the tone transmitted by a modem receiving a call to the modem that called it, which initiates the  
handshaking between the two modems.) At higher speeds there is no conflict, because all use CCITT  
frequencies. At lower speeds (0-1200 bps), in the U.S., some modems use the Bell frequency of  
2225 Hz. However, the CCITT specification for V.22 has an answer tone frequency of 2100 Hz.  
The ATB0 command enables CCITT frequencies including V.21 (300 bps) and V.23 (1200/75 bps).  
The ATB1 command enables Bell frequencies including Bell 103 (300 bps). The modem default is  
ATB0. This command is not used in BLK models.  
Phone Line Monitoring Speaker M  
The modem has an internal on-board, speaker which functions like the speaker in a telephone  
handset to enable you to monitor phone line activity. The M command can be used to determine  
when the speaker is operational.  
Entering ATM0 disables the speaker completely, while ATM1 causes the speaker to be on only until  
a carrier signal is detected. ATM2 causes the speaker to remain on at all times. ATM3 causes the  
speaker to be on during dialing and off during handshake. ATM1 is the default setting, and the one  
that should be used in most applications.  
Enable or Disable Recognition of Remote Digital Loop Signal &T  
The modem has several self-test features (covered in Chapter 8). The tests are activated with  
different U commands, such as ATU1, and so forth. The &T command is a phone line conditioning  
command that enables or disables the modem’s ability to recognize the Remote Digital Loop (RDL)  
test signal.  
The AT&T4 command lets the modem respond to a RDL signal, and places itself in digital loop. The  
AT&T5 command causes the modem to ignore the RDL signal. The factory default is &T5.  
Enable/Disable Trelis Coded Modulation #T  
This command enables or disables the Trellis Coded Modulation of the modem. There is usually no  
need to disable (turn off) Trellis codings except under an unusual line condition called impulse noise.  
AT#T0 turns Trellis coding off and AT#T1 turns Trellis coding on (factory default).  
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Chapter 5 - Command Mode  
Fallback Modes When On-Line #F  
If line conditions deteriorate, the modem automatically drops its transmission speed (“fallback”). The  
#F command controls the different ways the modem falls back. During operation, if the error rate  
becomes too great, the modem performs a retrain. If after the retrain, the error rate is still too high for  
33600 bps (19200 bps for 1932 models, 14400 bps for 1432 models) operation, the modem initiates a  
retrain at 4800 bps. If after the first retrain the modem returns on line at 33600 bps (19200 bps for  
1932 models, 14400 bps for 1432 models), the modem then starts a counter and a timer. If three  
retrains occur within a two minute period, the modem falls back to 4800 bps.  
Entering AT#F0 (or AT#F) allows no fallback when on-line.  
AT#F1 allows the modem to fallback (based on the error rate or if three retrains have occurred within  
a two minute period) from:  
2834 Series: 33.6K to 31.2K to 28.8K to 26.4K to 24K to 21.6K to 19.2K to 16.8K to 14.4K to 12K  
to 9.6K to 4.8K bps.  
1932 Series: 19.2K to 16.8K to 14.4K to 12K to 9.6K to 4.8K bps.  
1432 Series: 14.4K to 12K to 9.6K to 4.8K bps.  
The AT#F2 command enables incremental fall back, but also enables incremental fall forward if the  
phone line improves. AT#F2 is the factory default setting.  
Enable/Disable Lowspeed Fast Connect $FC (2834 Series only)  
Entering AT$FC0&W0<CR> sets up the data pump so that it will not transmit a 5 second 2100 Hz  
signal. Entering AT$FC0&W0<CR> allows the modem to transmit a 5 second 2100 Hz signal and is  
the factory default.  
Cleardown at Disconnect &CD (2834 Series only)  
The &CD command is used for control of cleardown at disconnect in V.32, V.32bis, V.34 and V.34  
enhanced modes.  
A cleardown usually adds 1-2 seconds to the time it takes for the modem to go on-hook after a  
disconnect. A cleardown makes a disconnect by the remote modem easier to detect and a  
subsequent re-connection more likely. Enter AT&CD0&W0<CR> to execute a cleardown at  
disconnect (default); and enter AT&CD1&W0<CR> to disable the cleardown function.  
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Auto Speed Detect #A  
The function of the #A command is to detect and select the operational data rates (the “starting”  
speeds) with which the modem uses for initial handshake and speed selection.  
Remember, this command does not control the originating data rate of the modem (that is done by  
the Modem Baud Rate command $MBn), but only the Answer mode “starting” speeds.  
Entering AT#A0 (or AT#A) causes the modem to operate starting at:  
2834 Series: 33,600 bps, with fallback to 28,800 to 19,200 to 14,400 to 9600 to 4800 to 2400 to 1200  
and to 300 bps.  
1932 Series: 19,200 bps, with fallback to 14,400 to 9600 to 4800 to 2400 to 1200 and to 300 bps.  
1432 Series: 14,400 bps, with fallback to 9600 to 4800 to 2400 to 1200 and to 300 bps.  
Entering AT#A1 causes:  
2834 Series: 33,600 bps operation only.  
1932 Series: 19,200 bps operation only.  
1432 Series: 14,400 bps operation only.  
Entering AT#A2 causes the modem to operate at starting speeds of:  
2834 Series: 33,600 bps, with incremental fallback to 28,800, 19,200, 14,400, 9600 and 4800 bps.  
1932 Series: 19,200 bps, with incremental fallback to 14,400, 9600 and 4800 bps.  
1432 Series: 14,400 bps, with incremental fallback to 29600 and 4800 bps.  
The AT#A3 command causes the modem (all models) to begin operation as a V.22bis modem at  
2400 bps, with fallback to 1200 to 300 bps. AT#A0 is the factory default value.  
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Chapter 5 - Command Mode  
5.4.7  
RS-232C Interface Control Commands  
Carrier Detect Control &C  
The &C command allows you to control the status of the Carrier Detect signal (CD-Pin 8) on the RS-  
232C line. You have four choices.  
You can force the signal high, or allow it to act normally, or force the modem to reset when CD drops,  
or set it to stay high until the modem disconnects, go low momentarily, and then go high again. The  
last option is useful with some CBX phone systems and mainframe front ends, which require CD to  
act in this manner.  
To allow CD to act normally, enter the command AT&C1 (the factory default setting). To force CD on,  
enter AT&C0. To reset the modem to its current parameters when CD drops, enter AT&C4. To set  
up CD so that it drops for one second on disconnect and then comes up again, enter AT&C2. (If you  
want the drop time to be something other than one second, use S-Register S24 to change this value.  
Refer to the Chapter 6 instructions for S24.  
Data Terminal Ready Control &D  
Data Terminal Ready (DTR) on pin 20 of the RS-232C interface is required in order for the modem to  
operate. A high DTR signal tells the modem that the device to which it is connected is active, or  
"ready" to communicate through the modem. If the signal is not being provided on the RS-232C  
interface, you can force DTR high with DIP-Switch #1 (Chapter 9).  
DTR has some other modem functions. DTR can be used to trigger a dialing sequence, called DTR  
Dialing. The condition of DTR can also be used to cause the modem to reset to its default  
parameters, just as if you had given the modem an ATZ command. To do this, enter the command  
AT&D3 and hit RETURN.  
The modem will now reset itself whenever DTR is dropped from On to Off, and will also go on-hook  
(hang up) if it is on-line.  
Entering AT&D0 or AT&D causes the modem to ignore DTR. Entering AT&D1 causes the modem to  
go on-hook (hang up) with loss of DTR. The modem enters Command mode when DTR goes high  
again. Auto-answer is disabled while DTR is low. Entering AT&D2 causes the modem to go on hook  
with loss of DTR. The modem enters command mode when DTR goes high again.  
CTS Control &R  
The &R command allows you to control the Clear to Send signal (CTS-Pin 5) on the RS-232C  
interface. You have three choices. You can force the CTS signal high, allow it to act normally, or set it  
to stay high until the modem disconnects, go low momentarily, and then go high again. The last  
option is useful with some CBX phone systems and mainframe front ends, which require CTS to act  
in this manner.  
To allow CTS to act normally, enter the command AT&R0. To force CTS on, enter the command  
AT&R1 (this is the factory default setting). When the modem goes on-line, CTS still provides flow  
control. To set up CTS so that it drops for one second on disconnect and then comes up again, enter  
the command AT&R2. (If you want the drop time to be something other than one second, use S-  
Register S24 to change this value. Refer to Chapter 6).  
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MultiModemBL User Guide  
Data Set Ready Control &S  
The &S command allows you to control the status of the Data Set Ready signal (DSR - pin 6) on the  
RS-232C interface. You have three choices. You can force the signal high, allow it to act normally, or  
set it to stay high until the modem disconnects, go low momentarily, and then go high again. The last  
option is useful with some CBX phone systems and mainframe front ends, which require DSR to act  
in this manner.  
To allow DSR to act normally, enter the command AT&S1 (the default setting). To force DSR on,  
enter the command AT&S0. To set up DSR so that it drops for one second on disconnect and then  
comes up again, enter AT&S2. If you want the drop time to be something other than one second, use  
S-Register S24 to change this value (Refer to Chapter 6).  
CTS/RTS Interaction Control &RF  
In typical operation, Clear to Send follows Request to Send when the modem is on-line. In other  
words, if RTS goes off, CTS goes off in response. The &RF0 command enables CTS to follow RTS.  
In some applications, however, it may be necessary for CTS to operate independent of RTS. &RF1  
allows CTS to operate independently regardless of the state of RTS, and is the factory default. If this  
is the case, refer to the &R command for control of the Clear to Send signal.  
DSR/CD Interaction Control &SF  
In typical applications, Data Set Ready (DSR) follows Carrier Detect (CD). &SF0 enables DSR to  
follow CD, and is the factory default. &SF1 enables DSR to operate independent of CD. If this is your  
application, refer to the &S command for control of the Data Set Ready signal.  
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Chapter 5 - Command Mode  
5.4.8  
Error Correction Commands  
You can use AT commands to place your modem one of three V.42 (error correction) modes of  
operation. These are the Normal, Auto-Reliable, and Reliable modes.  
Normal Mode &E0  
In Normal mode of operation, the modem’s V.42 error correction capabilities are disabled, and the  
modem functions as a non-error-correcting modem.  
Auto-Reliable Mode &E1  
In Auto-Reliable mode during the handshaking procedures at the start of the on-line connection, the  
modem automatically determines whether or not the modem with which it is communicating is using  
V.42 error correction. If the modem determines that the other modem is using V.42, it switches itself  
into MNP or LAPM Reliable (V.42) mode and its error-correction capability is enabled. If it is  
determined that the other modem is not using V.42, the modem remains in Normal mode, without  
error correction. The default setting is Auto-Reliable mode (&E1).  
The method the modem uses to determine if the modem it calls is a V.42 modem involves the use of  
a “Link Request”.  
When the modem is in Auto-Reliable mode and originates a call, it goes through normal handshaking  
procedures just like any dial-up modem. After establishing the on-line connection, the modem  
transmits a Link Request message to the answering modem. (The Link Request message is  
generally about 33 coded characters.) If the answering modem replies with an appropriate V.42  
acknowledgment response, the modem switches into Reliable mode. Otherwise it stays in Normal  
mode. This V.42 Link Request handshaking procedure generally takes about five seconds.  
When operating in V.42 Reliable mode, the modem uses its memory, or buffer, to store data as it is  
received. During periods of error-caused retransmissions or compression slowdowns, this buffer may  
fill up. To prevent buffer overflow and subsequent loss of data, the modem uses "flow control" to  
signal the computer attached to its RS-232C port that the modem buffer is close to being full. This  
causes the computer to pause in its data transmission until the modem is able to empty its buffer  
sufficiently to accept more data, at which time the modem signals the computer that it may resume  
transmission. (Flow Control is discussed in Section 5.4.9).  
Reliable Mode &E2  
In Reliable mode, the modem uses its V.42 error correction capabilities during all transmissions, and  
must be connected to another modem with a similar protocol activated (MNP or LAP-M).  
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V.42 Mode Select #L  
The V.42 standard implements both MNP Class 3 & 4 and LAP-M error correction methods. The V.42  
Mode Select command (#L) selects which type of error correction (MNP or LAP-M) your modem  
uses for transmissions.  
The various #L command options are as follows.  
#L0 Command  
The #L0 Command allows a pair of modems to negotiate which V.42  
mode (MNP or LAP-M) will be used in their transmissions.  
Originate Mode  
a. If both modems have LAP-M capability, the modems use LAP-M  
mode.  
b. If one or both modems do not have LAP-M capability and both  
have MNP, the modems use the MNP mode.  
Answer Mode  
a. The answering modem responds to either an MNP Link Request  
or LAP-M Originator Detection Pattern (ODP) signal depending on  
which the originating modem issues.  
#L1 Command  
#L2 Command  
#L3 Command  
The #L1 Command sets your modem to MNP error correction and  
disables LAP-M. This command is for Originate mode only. In  
Answer mode, the modem still accepts MNP or LAP-M.  
The #L2 Command sets your modem to LAP-M error correction, and  
disables MNP. This command is for Originate mode only. Answer  
mode still accepts MNP or LAP-M.  
In the prior commands, the modems use a two phase process to  
establish a V.42 connection (detection to establish whether the  
remote modem is also error correcting, and then protocol  
establishment to determine parameters and to establish the error  
correction connection). If you know that the other modem is a V.42  
error correcting modem, and you wish to use LAP-M, the #L3  
command disables the detection phase and goes directly to protocol  
establishment. Both modems must have #L3 in effect.  
Auto-Reliable Buffering $A  
In Auto-Reliable mode, the modem is given four seconds to establish a Reliable connection. After this  
four-second period, the modem drops to Normal mode. Any data which is received during this period  
is typically discarded. The $A command can be used to cause the modem to buffer (save) data that  
is received during this Auto-Reliable time-out period. This data will then be output by the modem after  
the CONNECT message.  
AT$A0 = Discard data received during auto-reliable time period.  
AT$A1 = Buffer data received during auto-reliable time period.  
The factory default is $A0.  
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Chapter 5 - Command Mode  
Enable/Disable Auto Reliable Fallback Character $F  
In Auto-Reliable mode, the modem is given four seconds to establish a Reliable connection. If a  
single CARRIAGE RETURN is received from the remote modem during this four second period, the  
Auto-Reliable modem assumes that the remote modem is not in Reliable mode and drops to Normal  
(non-error correcting) mode. The CARRIAGE RETURN is the only character which causes the  
modem to drop to Normal mode. Any other character will either be buffered or discarded.  
The $F command can be used to disable this fallback-to-Normal-due-to-CARRIAGE-RETURN  
feature.  
The Auto-Reliable fallback character ($F) and Auto Reliable buffering ($A) commands can be used  
together to cause the modem to buffer all data received up until the CARRIAGE RETURN, and then  
drop to Normal mode. All data received will then be output following the CONNECT message.  
AT$F0 = Do not fall back to Normal if CARRIAGE RETURN received.  
AT$F1 = Fall back to Normal mode if CARRIAGE RETURN received.  
The factory default is $F0.  
Retransmit Count $R  
If errors are received during a Reliable connection, the modem re-sends the block of data which  
contained an error. With the $R0 command, if another error occurs, the block will be re-sent again.  
The modem counts the number of times that a data block is re-sent. If the same block of data is  
resent 12 times and still has not been received properly, the modem assumes that the transmission  
line is unsuitable for transmission, and abort the connection.  
This retransmit counter is disabled by the $R1 command. When the retransmit counter is disabled,  
the modem keeps trying to send data and will not abort, no matter how many times the same block is  
resent.  
AT$R0 = Disconnect if retransmit count is exceeded.  
AT$R1 = Do not disconnect due to retransmits.  
The factory default setting is $R0.  
V.42 Error Correction/300bps $E  
At 300 bps, error correction is not typically used. $E1 lets the modem function at 300 bps in either  
Normal (&E0), Auto-Reliable (&E1) or Reliable (&E2) mode. $E0, which is the modem’s default,  
disables 300 bps/V.42 error correction altogether.  
AT$E0 = No V.42 Error correction at 300 bps.  
AT$E1 = V.42 Error Correction at 300 bps.  
The factory default setting is $E0.  
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MultiModemBL User Guide  
5.4.9  
Flow Control Commands  
Flow control refers to the techniques used by computer devices to stop and restart the flow of data to  
and from each other. Flow control is necessary so that a device does not receive more data than it  
can handle. In the case of the MultiModem, there is a need for flow control in both directions. As  
illustrated on the next page, flow control for data passing from your computer to the modem is called  
Modem-Initiated Flow Control and flow control for data passing from the modem to your computer is  
called Computer/Terminal-Initiated Pacing.  
The MultiModem supports both hardware and software Modem Initiated Flow Control. On the  
Computer/Terminal-Initiated Pacing side, it supports hardware and software flow control, and a  
special version used by Hewlett-Packard compatible systems called ENQ/ACK Pacing. The modem  
allows hardware and software pacing to be passed through the modem to the other end of the link so  
that your computer or terminal can control data start/stop activity through your modem.  
This is called Xon/Xoff Pass-Through. To state it simply, “Flow Control” is something the modem  
does to the computer, while “Pacing” is something the computer does to the modem.  
Modem-Initiated Flow Control  
Computer  
or  
Terminal  
RS-232/V.24  
Data Flow  
Modem  
Computer-Initiated Flow Control Pacing  
Computer  
or  
Terminal  
RS-232/V.24  
Modem  
Data Flow  
Figure 5-2. Flow Control and Pacing  
Hardware Flow Control &E4  
With Hardware Flow Control, the modem uses its RS-232C interface to control the flow of data from  
the computer or terminal to which it is attached. The CTS (Clear to Send) signal on Pin 5 of the RS-  
232C interface is brought low to stop the flow of data, and is brought high to restart it. When you  
select Hardware Flow Control as your Modem Initiated Flow Control method, you will also be  
selecting it for Pacing.  
The difference between the two, however, is that Modem-Initiated Flow Control uses the Pin 5 CTS  
output signal, while Pacing uses the Pin 4 RTS input signal.  
Modem commands are used to select the method of flow control used by the modem when its error  
correction capabilities are used. These commands are covered in Section 5.4.9. If neither method is  
selected, the modem defaults to no flow control (&E3).  
Xon/Xoff Flow Control &E5  
Xon/Xoff is the most commonly used method of flow control. Under this method, control characters  
known as “Xon” and “Xoff” are inserted by the modem into the data to start and stop the flow of data  
from the computer or terminal to which the modem is attached. Xoff, which is a Control-S, stops the  
flow of data, and Xon, which is a Control-Q, restarts it. With regard to Binary Data, Xon/Xoff flow  
control is not recommended because an Xoff character may be part of the data and would trigger an  
Xoff of the modem or software package, which would halt data flow.  
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Chapter 5 - Command Mode  
Xon/Xoff Pass-Through &E7  
So far, you have had three choices to make regarding pacing:  
1. You can set the modem to respond to Xon/Xoff pacing.  
2. You can set the modem to respond to RTS pacing.  
3. You can set the modem to ignore pacing completely.  
Well, we’re not done with pacing yet. There’s another choice you can make (which actually can apply  
to both pacing and modem-initiated flow control, although it applies mainly to pacing) and that is  
something called Xon/Xoff Pass-Through.  
This means that if your modem is set to respond to Xon/Xoff commands, you can have the modem  
do one of the following:  
1. The modem responds to the Xon and Xoff pacing commands while at the same time allowing  
these commands to pass through the modem and on to the remote location. We call this  
“Respond, Pass-Through”.  
2. The modem responds to Xon/Xoff pacing, but does not allow the pacing signals to pass through  
the modem and on to the remote location. We call this “Respond, No Pass-Through”.  
When Xon and Xoff commands are allowed to pass through the modem, the computer or terminal at  
the remote site will receive these commands, and depending on how it is configured, the computer or  
terminal may respond to them also.  
When two MultiModems are connected in Normal mode (not using error correction), Xon/Xoff can be  
used to control the flow of data between the modems. Flow Control can be turned on or off with the  
Normal Mode Modem Flow Control commands. When the modems are connected in Reliable mode,  
a different method of modem Flow Control is used, and the commands for Normal Mode Modem  
Flow Control are ignored.  
When you are using Speed Conversion in Normal Mode, you must activate the modem’s Normal  
Mode Modem Flow Control (Speed Conversion is explained in Section 5.4.11).  
Send Xon/Xoff Characters #X  
The #X phone interface command allows the modem to send either a single or multiple Xoff  
characters at the modem's buffer full level. When the modem’s buffer reaches it's "buffer full" level,  
the next character received causes another Xoff to be sent for every character subsequently received  
by the modem.  
The AT#X0 command (factory default setting) causes one Xoff to be sent until the buffer reaches the  
Xon level. The AT#X1 command causes an Xoff to be sent for every character received after the  
modem reaches its buffer full level.  
Hewlett-Packard ENQ/ACK Pacing &E9  
If the modem is being used with Hewlett Packard (or similar) equipment that employs ENQ/ACK  
pacing, the modem can be configured to respond to ENQ/ACK commands, making it compatible with  
HP systems. Doing so does not affect any other flow control or pacing already configured in the  
modem.  
When configured for ENQ/ACK, the ENQ (Control-E) and ACK (Control-F) signals from the HP  
equipment will be accepted and responded to according to Hewlett-Packard protocol.  
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MultiModemBL User Guide  
Normal Mode Modem Flow Control On &E11  
When two MultiModems are connected in Normal mode (not using error correction), Xon/Xoff can be  
used to control the flow of data between the modems. Flow Control can be turned on or off with the  
Normal Mode Modem Flow Control commands. When the modems are connected in Reliable mode,  
a different method of modem flow control is used, and the commands for Normal Mode Modem Flow  
Control are ignored.  
When you are using Speed Conversion in Normal Mode, you must activate the modem’s Normal  
Mode Modem Flow Control (Speed Conversion is explained in Section 5.4.11).  
Terminal/Computer Initiated Pacing &E13  
As mentioned earlier, the modem can initiate flow control by issuing Xon/Xoff commands or toggling  
the CTS signal on the RS-232C interface. The modem can also be configured to react to similar  
commands and signals from the computer or terminal to which it is attached via the RS-232C  
interface. We refer to the computer or terminal initiated flow control as Pacing. When the modem is  
set for Pacing On, the modem will respond to the terminal or computer pacing. When the modem is  
set for Pacing Off, it will ignore pacing.  
In order for the modem to be set for Pacing On, a modem-initiated method of flow control must be  
previously selected. Once this is done, the modem will respond to either Xon/Xoff commands, or to  
the toggling of the RTS (Request to Send) signal on Pin 4 of the RS-232C interface, depending on  
what you selected earlier as your Modem-Initiated Flow Control method.  
Maximum Block Size &BS  
The maximum size of Reliable mode data blocks can be controlled with the &BS command. MNP 3  
sends blocks of 1 to 64 characters. MNP 4 and 5 typically send blocks of 1 to 256 characters and  
LAP-M typically send 128 characters. For MNP Classes 4 and 5/LAP-M, reducing the block size to  
64 characters may give a smoother flow of data, and better throughput on noisy phone lines. Using  
smaller block sizes over good phone lines may cause a slight loss in throughput (speed).  
AT&BS0 = Maximum transmit block size of 64 characters  
AT&BS1 = Maximum transmit block size of 128 characters (LAP-M) 256 characters (MNP)  
The factory default setting is &BS1.  
Parity Selection #P  
The #P command enables the setting of parity. AT#P0 selects no parity. AT#P1 selects odd parity.  
AT#P2 selects even parity and is the default value. Note when setting up your data comm software, it  
is critical that both your remote and local system's parity selection be set identically.  
AT#P0 = no parity  
AT#P1 = odd parity  
AT#P2 = even parity  
The factory default setting is AT#P2.  
68  
 
Chapter 5 - Command Mode  
5.4.10 Compression, Error Correction, Flow Control, Pass-  
Through and Pacing Commands  
The modem has a variety of commands to control its error correction and data compression options.  
These additional commands are listed below. (Remember to precede each command with the AT  
characters.)  
Normal/Auto-Reliable/Reliable Mode Commands:  
&E0 = Normal Mode  
&E1 = Auto-Reliable Mode*  
&E2 = Reliable Mode  
Modem-Initiated Flow Control Commands:  
&E3 = Disables flow control (no flow control)  
&E4 = Hardware flow control (CTS on/off and RTS on/off)*  
&E5 = Xon/Xoff flow control  
Xon/Xoff Pass-Through Commands:  
&E6 = Modem responds to Xon/Xoff characters, but does not allow Xon/Xoff characters to pass  
through to remote site.*  
&E7 = Modem responds to Xon/Xoff characters, and allows them to pass through to remote site.  
#X0 = Selects single Xoff character until Xon level returns*  
#X1 = Selects multiple Xoff characters after buffer levels is full.  
Enq/Ack Pacing Commands:  
&E8 = Enq/Ack method of pacing off*  
&E9 = Enq/Ack method of pacing on  
Normal Mode Modem Flow Control Commands:  
&E10 = Normal Mode Modem Flow Control off*  
&E11 = Normal Mode Modem Flow Control (Xon/Xoff) on  
Computer-or Terminal-Initiated Flow Control (Pacing) Commands:  
&E12 = Pacing off*  
&E13 = Pacing on (either RTS on/off or Xon/Xoff depending on the setting of &E4 or &E5).*  
Data Compression Commands:  
&E14 = Data Compression disabled  
&E15 = Data Compression enabled*  
*Factory Default setting  
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MultiModemBL User Guide  
5.4.11 Speed Conversion Commands  
Speed conversion is a necessary part of data compression since data must be presented to the  
modem faster than it can handle data, if data compression is to be effective.  
Speed conversion allows the modem to communicate at one speed over the phone line, and at  
another speed at the RS-232C interface. The speed (also referred to as “data rate” or “baud rate”)  
can be fixed at the RS-232 interface independently of the baud rate of the on-line transmissions.  
In addition to data compression, another popular application for speed conversion involves an auto-  
answer MultiModem connected to a computer that does not have autobaud capability. This means  
that the computer must be set at a fixed baud rate, regardless of the baud rate that the modem is  
communicating over the phone line at. In this application, speed conversion allows the modem to  
match its speed to that of the calling modem, while at the same time communicating with the  
attached computer through its RS-232C port at a fixed baud rate, which can be pre-selected at 300,  
1200, 2400, 4800, 9600, 19,200, 38,400, 57,600 or 115,200* bps.  
(* 1932 and 2834 models only)  
Speed Conversion $BA  
When using speed conversion, you must set the modem so that it does not adjust its speed at the  
RS-232C serial port, even if the modem does adjust its data rate. To turn Speed Conversion ON,  
enter the command AT$BA0 and hit RETURN.  
To turn Speed Conversion OFF, enter AT$BA1 and hit RETURN. The modem will now match its RS-  
232C speed to that of the computer, and will adjust its speed to any changes in the computer’s speed  
in Originate mode, or to the speed of the originating modem in Answer mode. The speed at which the  
modem communicates over the phone line will always be the same as the speed at which it  
communicates via its RS-232C serial port.  
Modem Baud Rate $MB  
The $MB command presets the modem’s transmission baud rate for originate operations, (i.e., the  
speed of the modem’s transmissions over the telephone lines when originating a call). With speed  
conversion, this transmission speed can be a different baud rate than the serial port speed.  
When the modem receives (answers) a call from another modem, it automatically switches its phone  
line transmission speed to match the calling modem. However, if the modem originates a call to  
another modem that is unable to connect at the same baud rate, it automatically drops to a lower  
baud rate in an attempt to match the speed of that modem. For example, if the modem is set for  
14,400 baud and calls another modem that has a top speed of 2400 baud, it drops to 2400 baud.  
The command to set the Modem Baud Rate is AT$MBn, where n can be:  
2834 Series:  
AT$MB75  
AT$MB300  
=
=
=
=
=
=
=
=
=
=
CCITT V.23  
300 bps  
AT$MB1200  
AT$MB2400  
AT$MB4800  
AT$MB9600  
AT$MB14400  
AT$MB19200  
AT$MB28800  
AT$MB33600  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
14400 bps  
19200 bps  
28800 bps  
33600 bps  
The factory default is 33600 bps.  
70  
 
Chapter 5 - Command Mode  
1932 Series:  
AT$MB75  
=
=
=
=
=
=
=
=
CCITT V.23  
300 bps  
AT$MB300  
AT$MB1200  
AT$MB2400  
AT$MB4800  
AT$MB9600  
AT$MB14400  
AT$MB19200  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
14400 bps  
19200 bps  
The factory default is 19200 bps.  
1432 Series:  
AT$MB75  
=
=
=
=
=
=
=
CCITT V.23  
300 bps  
AT$MB300  
AT$MB1200  
AT$MB2400  
AT$MB4800  
AT$MB9600  
AT$MB14400  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
14400 bps  
The factory default is 14400 bps.  
71  
 
MultiModemBL User Guide  
Serial Port Baud Rate $SB  
The $SB command presets the speed of the modem’s serial (RS-232C) port, in both Originate and  
Answer modes. Speed conversion allows you to set this serial port baud rate at a fixed speed of up to  
115,200 bps for 1932 and 2834 models, and 57600 bps for 1432 models, regardless of the modem’s  
transmission speed setting.  
In order for this command to be effective, the modem’s Speed Conversion feature must first be  
turned off with the $BA command. When Baud Adjust is on, the modem automatically adjusts its  
serial port baud rate to match the speed of the computer or terminal it is connected to, as soon as it  
receives its first AT command. However, in many applications, such as automatic answer, the  
modem may not receive AT commands, in which case it is very useful to be able to preset the serial  
port baud rate with this $SB command.  
In addition to setting the modem’s serial port speed, this command also sets the speed at which the  
modem issues Command mode responses.  
The modem will accept AT commands at any speed, regardless of the speed preset by the $SB  
command. If the modem receives such a command at a speed that is different than the preset speed,  
the modem switches its serial port baud rate to match the new AT command speed, although the  
baud rate value stored by the $SB command remains the same. This provides you with a convenient  
way to switch the serial port speed, and still make it easy to go back to the original speed  
automatically the next time the modem is powered up or reset with an ATZ command.  
The command to set the Serial Port Baud Rate is AT$SBn, where n can be:  
AT$SB300  
=
=
=
=
=
=
=
=
300 bps  
AT$SB1200  
AT$SB2400  
AT$SB4800  
AT$SB9600  
AT$SB19200  
AT$SB38400  
AT$SB57600  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
19,200 bps  
38,400 bps  
57,600 bps  
115,200 bps*  
AT$SB115200 =  
The factory default is 57,600 bps.  
(* 1932 and 2834 Series only)  
Note: Some serial ports, particularly those in older PC-compatible computers, may limit the  
performance of a higher speed modem like the MultiModem (see Chapter 3). The limiting factor is a  
circuit called a Universal Asynchronous Receiver/Transmitter, or UART. All data from your modem  
flows through it. 8250, 16450, and 16550 are UARTs typically used in PC-compatible computers. The  
8250 is unreliable above 9,600 bps and the 16450 is unreliable above 19,200 bps. The 16550 UART,  
however, is reliable to at least 115,200 bps. With V.42bis data compression enabled, the MT2834BL  
can achieve throughputs approaching 115.2K (depending on line quality and file content). If you  
presently do not have a 16550 UART in your PC, we recommend that it be replaced with a Multi-Tech  
high speed Intelligent Serial Interface (ISI) card. It comes in one, two and eight-port versions for  
DOS/Windows and UNIX systems, and includes a 32 K buffer that eliminates data loss even at high  
speeds. See your dealer for details.  
72  
 
Chapter 5 - Command Mode  
5.4.12 Immediate Action Commands  
Help Screens $H  
The Help command is designed to give you short explanations on how to use each modem  
command. The Help command can be quite useful if your manual is not handy and you are in the  
middle of a communications session. Although the explanations are quite abbreviated compared to  
those in this manual, they should prove to be helpful reminders when needed.  
At the time of this writing, we have three screens of Help information (Screen #1, #2 and #3), and  
more screens may be added in the future. The Help commands are structured so that you can call up  
one of three Help screens, as follows:  
AT$H1 = Help Screen #1  
AT$H2 = Help Screen #2  
AT$H3 = Help Screen #3  
Inquiry for Product Code I  
Some systems or software packages automatically check the “identification” of the modem with which  
they are communicating, by using the I command. This “read” command lets the software to  
determine the type of modem with which it is communicating.  
When ATI or ATI0 is entered, the modem responds with 247. When ATI1 is entered, the modem  
responds with a three-digit code indicating the firmware version number. When ATI2 is entered, the  
modem responds with MT2834BL, MT1932BL or MT1432BL depending on model.  
Windows 95 Autodetect Inquiry I9 (2834 Series only)  
This read command permits a Windows 95 operating system to query the MT2834BL's  
characteristics. When ATI9<CR> is entered the symbols BL 28800 FAX CT are displayed; which  
indicates to the Windows 95 system that your particular modem is a MT2834BL, 28,800 bps, fax  
Class 2 capable modem. With autodetect support in your MT2834BL, your PC can automatically  
allocate resources and configure it and other devices. The MT2834BL implements autodetect  
capability in the form of a single .INF (Information) file that specifies AT Command mode and Result  
Code "Registry Keys" that are specific to your MT2834BL.  
Listing Current Operating Parameters L5 L7  
The L5 and L7 commands list the current operating parameters of your modem. This information can  
be very useful when you are changing communications software or when you are changing modem  
default settings.  
The command to list the modem’s current operating parameters is ATL5 for the basic parameters.  
Entering ATL7 lists additional parameters on the modem.  
Listing S-Register Values L6  
Entering ATL6 lists the current values stored in the modem’s S-Register. This information can be  
very useful if you wish to change S-Register values. (Refer to Chapter 6 for more information on S-  
Registers).  
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MultiModemBL User Guide  
Listing On-Line Diagnostics L8  
The L8 command displays the current on-line CONNECT status of the modem. This display can be  
printed and used as a modem status report or as diagnostic information (such as when calling Tech  
Support). To activate this command first type +++AT<CR>(on-line escape command while  
maintaining command mode), then type ATL8. What then displays on your monitor is your modem's  
current on-line condition (e.g., Link Type, Line Speed, Serial Speed, Type of Error Correction/Data  
Compression, Number of past Retrains, etc.).  
Off Hook H  
You can make the modem hang up (go On Hook). Entering ATH1<RETURN> brings the line Off  
Hook, just as if you picked up the telephone set. You can hang up by entering ATH0 or ATH (the  
default is 0 when no number is entered).  
Escape Sequences- Entering Command Mode While Still On-Line +++AT<CR>  
It is possible to cause the modem to enter Command mode after the modem has gone on-line with a  
remote modem, without disconnecting the call. This is done by entering an Escape Code. The default  
Escape Code used by the modem is three plus signs (+++) followed by the letters A and T, up to  
sixty command characters (most typically “H”, to hang up), and a RETURN. The number of  
command characters allowed after +++ AT<CR> , is defined by S-Register S34. S-Register S34  
defaults to ten command characters.  
When this is done, the modem escapes to Command Mode, executes the command (if any), and  
then remain in Command mode. For example, to hang up the modem at the end of a call, enter  
+++ATH and hit RETURN. There is no need to incorporate pauses before and after the plus signs,  
as done in earlier modems.  
BREAK AT<CR>  
The modem provides an alternative Escape method, using a Break signal as the Escape Code. The  
Break signal allows the start-stop DTE (data terminal equipment) to signal the modem without loss of  
character transparency. With this method, a BREAK signal is used instead of the three plus signs.  
The BREAK is followed by the letters A and T, up to 60 command characters, and RETURN. When  
this is done, the modem executes that command, but remains in On-Line mode unless the command  
was to hang up and/or reset the modem (an H or Z), in which case the modem would be in the  
Command Mode after executing that command.  
Escape Sequence Options - Entering Command Mode While On-Line %E  
As mentioned, the default escape sequence setting is for the modem to respond to the +++ escape  
method. Optional settings are for the modem to respond to the Break method, for the modem to  
respond to either the +++ or the Break Methods, for the modem to ignore both methods and not  
escape, for the modem to respond with no "OK" to +++, and for the modem to respond with "OK" to  
+++. The %E command is used to select these options, as follows:  
%E0  
%E1  
%E2  
%E3  
%E4*  
%E5*  
=
=
=
=
=
=
Modem Won’t Escape  
+++ AT<CR> Method (default)  
Break Method  
Either +++ or Break Methods  
No "OK" Response to +++  
"OK" Response to +++  
* The %E4 and %E5 commands enable or disable an "OK" response, which is required by some  
software packages during an escape sequence.  
74  
 
Chapter 5 - Command Mode  
Force Answer Mode A  
You can force the modem into Answer mode with the modem’s A command.  
Entering ATA when in Command mode immediately brings your modem off-hook, out of Command  
mode and into On-Line Answer mode, and causes it to transmit its carrier signal over the phone line.  
If no responding carrier tone is received by your modem within forty-five seconds (or some other time  
as determined by S-Register S7), your modem stops transmitting its tone, hangs up, and goes back  
into Command mode.  
Exiting Command Mode, Going Back On-Line O  
You can bring the modem out of Command mode and back into On-Line mode by entering ATO  
(where O is the letter O, not the number 0). In this case, the O command reverses what was done by  
entering the Escape Code. The O command will bring the modem into the same On-Line mode  
(Originate or Answer) that it was in prior to going into Command mode.  
5.4.13 Line Probe Commands (2834 Series only)  
Before V.34 negotiation takes place, remote and local modems transfer their functional capabilities  
using modulated calling and answering tones; indicating the common capabilities of the modem at  
each end.  
Once this is done, a probing signal is passed between the modems to identify impairments in the  
telephone channel (e.g., Receive Signal Strength vs. Frequency, Noise vs. Frequency and Signal to  
Noise Ratio vs. Frequency). After receiving the results of the probing signal, the modem receivers  
and transmitters begin with the lowest speed and move up until reaching the highest speed at which  
they can exchange data. All this occurs in about five seconds.  
There are a number of Line Probe Commands. These commands are configurable and can be stored  
to RAM (via AT&W0).  
These commands are listed below.  
Enable/Disable Reading of Line Probe Information Commands:  
%DP0 = Do not read Line Probe information from DSP during handshake (Default).  
%DP1 = Read Line Probe information from DSP during handshake.  
Format of Line Probe (Graph or Table) Commands:  
%DF0 = Data is displayed in Graph format. Y axis is shown in dBms (Default).  
%DF1 = Data is displayed in Table format. Numeric values are displayed for 150Hz to  
3750Hz in 75HZ increments.  
Immediate Action Line Probe Commands:  
To activate these commands first type +++AT<CR>(on-line escape command while maintaining  
command mode), then type the Command prefixed by an AT.  
&RP = This command initiates a retrain that makes the processor read Line Probe  
information. Valid only when on-line in V.34 mode.  
L9  
= Displays Signal Strength information.  
= Displays Signal to Noise Ratio information (SNR).  
= Displays noise information.  
L10  
L11  
75  
 
MultiModemBL User Guide  
76  
 
Chapter 6 - S-Registers  
 
MultiModemBL User Guide  
6.1 Introduction  
Certain Command Mode configurations are stored in memory registers called, S-Registers. The S  
command is used to assign a value to, and to read the current value of an S-Register. To assign a  
value to an S-Register, enter the letter S, followed by the S-Register number and an equals sign (=),  
and then a decimal response to the message “ENTER THE NEW VALUE IN DECIMAL FORMAT”.  
To read an S-Register value, enter the letter S followed by the S-Register number and a question  
mark (?), then hit RETURN. To verify that the S-Register value was entered correctly, enter for  
example, ATS8? and hit RETURN. You should receive a response of the assigned value given to  
that S-Register. Refer to Section 6.2, Reading and Assigning S-Register Values.  
S0  
Number of Rings Until Modem Answers  
Unit:  
1 ring  
Range:  
Default:  
Description:  
0-255  
1
S0 defines the number of rings the modem waits before answering an incoming call.  
The default value is one ring (Decimal 1), which means that the modem answers the  
call immediately after the first ring. The maximum number of rings that can be  
configured is 255. Setting the value to zero (0) disables auto-answer completely.  
S1  
Rings Which Have Occurred  
Unit:  
1 ring  
Range:  
Default:  
Description:  
0-255  
0
S1 counts the number of rings that have occurred. It is a “read” type of register and  
is seldom, if ever, used in typical operation. Each time an incoming ring signal is  
detected, S1 increases its value by one, up to a maximum of 255. If you set S1 to a  
value other than its default value of zero, or if the value is increasing with rings, this  
new value remains stored in S1 for eight seconds after the last ring is counted, after  
which time the value reverts to zero.  
S2  
Escape Code Character  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-127  
43 (+)  
S2 defines the escape code character. The default character is the plus (+) sign  
(Decimal 43), but may be set for any ASCII character. Setting an S2 value greater  
than 127 results in no escape character, and therefore no means of entering  
Command mode from On-line mode without breaking the on-line connection.  
S3  
Return Character  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-127  
13 (^M)  
S3 defines the character recognized as Carriage Return (RETURN) or “Enter”. S3  
may be set for any ASCII character.  
78  
 
Chapter 6 - S-Registers  
S4  
Line Feed Character  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-127  
10 (^J)  
S4 defines the character recognized as Line Feed. S3 may be set for any ASCII  
character.  
S5  
Backspace Character  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-127  
8 (^H)  
S5 defines the character recognized as BACKSPACE. S5 may be set for any ASCII  
character.  
S6  
Wait Time for Dial Tone  
Unit:  
1 second  
Range:  
Default:  
Description:  
2-255, 4-255**, 4-7***  
2, 4**,4***  
S6 sets the time the modem waits after the RETURN key is pressed before  
executing a dial command. The default setting is two seconds (Decimal 2).  
S7  
Time for Carrier (Abort Timer)  
Unit:  
1 second  
Range:  
Default:  
Description:  
1-255, 1-55*  
45, 55*  
S7 defines the Abort Timer (lack of carrier) delay time. The default value is 45  
seconds (Decimal 45). This means that, after dialing, the modem waits for a carrier  
signal for up to 45 seconds and, if none is detected, aborts the call. The maximum  
S7 value is 255.  
S8  
Pause Time for Comma  
Unit:  
1 second  
Range:  
Default:  
Description:  
0-255, 4-255**, 4-7***  
2, 4**, 4***  
S8 sets the length of the pause caused by a comma inserted in a dialing command.  
The default setting is two seconds, (or two units Decimal 2) or four seconds, where  
each unit is one second. S8 may be set for up to 255 seconds.  
S8 also sets the time the modem waits before retrying a call after detecting a busy  
signal. Some computer systems need more than two seconds to reset (in which case  
you should increase the value of S8).  
* Value for International and DOC units  
** Value for International units only  
***BLK models only  
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MultiModemBL User Guide  
S9  
Carrier Detect Response Time  
Unit:  
100 mSec.  
Range:  
Default:  
Description:  
1-255  
6
S9 sets the time delay between when the modem first detects a valid incoming  
carrier signal and when the modem turns on its Carrier Detect circuit. The default  
setting is 600 milliseconds, or six units of 100 mSec each (Decimal 6). S9 may be set  
for up to 25.5 seconds.  
S10  
Carrier Loss Disconnect Delay Time  
Unit:  
100 mSec.  
Range:  
Default:  
Description:  
0-255  
7
S10 sets the time a carrier signal must be lost before the modem disconnects. The  
default setting is 700 mSec, or seven units (Decimal 7) of 100 mSec. Maximum delay  
is 25.4 seconds (Decimal 254). Setting the S10 value to 255 causes the modem to  
not disconnect with loss of carrier. (This S-Register applies at speeds of 2400 bps  
and less.)  
S11  
Tone Dialing: Tone Spacing and Duration  
Unit:  
1 mSec.  
Range:  
Default:  
Description:  
1-255, 80-255*, 80-255***  
70, 80*, 80***  
S11 sets the speed of tone dialing (spacing and tone duration times). The default  
value is 70 units (Decimal 7) or 80 units, where each unit is one mSec, meaning that  
each tone is on for 70 mSec with a 70 mSec pause between each.  
The minimum S11 value allowed by most telephone systems is 50 mSec (50 units).  
Very few telephone systems can handle anything faster than that. The maximum S11  
value is 255 mSec (255 units).  
S13  
Remote Configuration Escape Character  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-127  
37 (%)  
S13 defines the remote configuration escape character (which becomes your  
modem’s remote configuration character). The default is three percent symbols  
(%%%). When the S13 character is entered three consecutive times from a remotely  
connected site, your modem responds with its Remote Configuration procedure.  
* Value for International and DOC units  
** Value for International units only  
***BLK models only  
80  
 
Chapter 6 - S-Registers  
S15  
Callback Time Delay  
Unit:  
Seconds  
10-255  
20  
Range:  
Default:  
Description:  
S15 defines the time delay between Callback attempts after initial passwords have  
been exchanged between modems. Refer to Chapter 7 for Callback Security  
information.  
S16  
Callback Attempts  
Unit:  
1 Attempt  
Range:  
Default:  
Description:  
1-255, 1-2***  
4, 2***  
S16 defines the number of attempts allowed after initial passwords have been  
exchanged between modems.  
S17  
Changing Break Time  
Unit:  
10 mSec.  
Range:  
Default:  
Description:  
0-2.5 sec  
250  
S17 defines the break time (space) sent to the local PC. The default is set for a 25 to  
250 mSec break. The break time can be changed in 10 mSec increments by  
increasing or decreasing the value of S17.  
S18  
Automatic Leased Line Restoral  
Unit:  
1 minute  
Range:  
Default:  
Description:  
10-255  
30 minutes  
When the modem is in dial backup mode, it periodically checks the lease line to see  
if it is operational and tries to restore the lease line if possible. S18 defines how often  
attempts occur. The default of S18 is 30 minutes and can be set in one minute  
increments from 10 to 255 minutes. Setting the S18 restoral under 10 minutes  
causes excessive breaks in dial-up operation.  
S19  
Dial-Back Timer  
Unit:  
1 minute  
Range:  
Default:  
Description:  
0-255  
1
S19 is a timer that begins when the lease line goes down. S19 specifies the duration  
of time the modem attempts to reestablish the lease line connection.  
* Value for International and DOC units  
** Value for International units only  
***BLK models only  
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MultiModemBL User Guide  
S24  
PBX/CBX Disconnect Drop Time for DSR/CTS/CD  
Unit:  
50 mSec.  
Range:  
Default:  
Description:  
0-255  
20  
Some PBX and CBX phone systems require the modem’s DSR, CTS, and/or CD  
signal(s) to behave in a certain manner when calls are disconnected. The modem’s  
&R, &S, and &C commands cause the modem to drop these signal(s) for a specified  
time period upon disconnect, and then bring the signal(s) up again. S24 defines the  
length of time that the signals drop. The default setting of 20 results in a one second  
drop time, which is what most PBX/CBX systems with this requirement need.  
S25  
DTR Dropout Time  
Unit:  
100 mSec.  
Range:  
Default:  
Description:  
0, 1 through 255  
0
S25 defines the amount of time that DTR must be dropped before the modem  
disconnects. Typically, a disconnect occurs when DTR is dropped for 50  
milliseconds or more. This dropout time can be increased, up to a maximum of 25.5  
seconds. The S25 unit value for zero is the default value of 50 mSec. For values  
from 1 through 255, the unit value is 100 mSec.  
S26  
Failed Password Attempts  
Unit:  
1 failed attempt  
Range:  
Default:  
Description:  
0-255  
0
S26 counts the number of times there has been a failed password attempt. For  
example, if you entered ATS26? the message 003 would be displayed, meaning  
someone has failed three times to gain access to your modem using its password  
security system.  
S29  
Local Inactivity Timer  
Unit:  
minutes  
Range:  
Default:  
Description:  
1-255  
20  
S29 defines the amount of idle time that can elapse between AT commands after the  
SETUP password has been entered. If this timer expires, the LOGIN and SETUP  
passwords will have to be re-entered. S29 only takes effect when the modem has  
been sent a #DB1 command, which secures the modem from local and remote  
configuration or dialing (i.e., no AT commands can be sent until the LOGIN and  
SETUP passwords have been entered).  
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S30  
Inactivity Timer  
Unit:  
1 min.  
Range:  
Default:  
Description:  
0-255  
0
S30 causes the modem to disconnect if no data is transmitted or received for a  
specified time. This timer runs during both Reliable and Normal error correction  
connections. The timer restarts any time a data character is passed through the  
serial port (either sent or received). If noise on the phone line causes an error to be  
received during Normal mode, this also restarts the timer. The default value is off (0).  
The inactivity timer is disabled by setting S30 to 0, which is the factory default  
setting.  
S32  
Time Elapse for Escape Sequence  
Unit:  
1 second  
Range:  
Default:  
Description:  
0-255  
20  
S32 sets the time period to validate the escape sequence. If the time interval expires  
before the escape sequence is employed (by hitting RETURN), the escape  
sequence is aborted. The default is 20 units.  
S34  
Buffer Length of Command Mode...After On-line Escape Sequence  
Unit:  
ASCII Character  
Range:  
Default:  
Description:  
0-60  
10  
If the number of characters after AT exceeds the S34 buffer length value, the buffer  
is cleared and the escape sequence is aborted.  
S36  
Time Between DTR Inactive and Modem Off-Hook  
Unit:  
1 Second  
Range:  
Default:  
Description:  
0-255 seconds  
0
The DTR Busy-out feature uses S-Register S36 to set the time between DTR  
inactive (low) and the modem going off-hook. S36 can be set in one-second intervals  
from 0 to 255 seconds. With the default setting of S36=0, DTR Busy-Out is disabled  
(i.e., DTR won't Busy-Out).  
S37  
Time Between DTR Active and Modem On-Hook  
Unit:  
1 Second  
Range:  
Default:  
Description:  
0-255 seconds  
5
S37 sets the time between DTR being active and the modem going on-hook (not  
busy). S37 will only function in conjunction with S36.  
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S48  
Program V.34bis Connect Speeds (2834 Series only)  
Unit:  
Range:  
N/A  
33, 31, 28, 26, 24, 21,19,16,14,12, 96 and 48  
Default:  
0
Description:  
Defines which speed modem connects within the scope of Enhanced V.34 mode  
(e.g., S48 = 26 means maximum connect speed is 26.4K). This register  
compensates for line conditions that have trouble supporting higher Enhanced V.34  
speeds (e.g., 33.6K, 31.2K, 28.8K, 26.4K, 24K...). The modem default is a value of 0,  
which indicates a connection attempt of 33.6K.  
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Chapter 6 - S-Registers  
6.2 Reading and Assigning S-Register Values  
The S command is used to assign a value to, and to read the current value of, an S-Register. To read  
an S-Register value, enter the letter S followed by the S-register number and a question mark (?),  
then hit RETURN. For example, entering ATS7? and hitting RETURN displays the value of S-  
Register S7 in a 3-digit decimal form. The number 8 would appear as 008, the number 30 would  
appear as 030, and the number 255 would appear as 255.  
To assign a value to an S-Register, enter the letter S followed by the S-Register number and an  
equals sign (=), and then a decimal response to the message “ENTER THE NEW VALUE IN  
DECIMAL FORMAT”. Convert all ASCII characters to their decimal equivalents before entering them.  
S-Register decimal values range from 0-127 for ASCII characters, or 0-255 for numeric values. A  
complete ASCII conversion chart is located in Appendix B of this manual.  
6.2.1  
Examples of Assigning Values  
1. Let’s say you wish to have longer pauses caused by the comma in a dial command; five seconds  
instead of two. Entering ATS8=5 assigns 5 as the value for S-Register S8 (meaning the modem  
pauses five seconds for a comma in a dial command).  
2. In a second example, let’s say that you wish to configure the modem to answer incoming calls  
after the 30th ring instead of after the first ring. To configure S-Register S0 with a value of 30,  
enter ATS0=30 and hit RETURN.  
3. In a third example, let’s say you are calling long distance to another country code, and it is taking  
a long time to connect. The S-Register S7 (Abort Timer) setting of 45 seconds, is insufficient.  
The abort timer times out and cancels the call before a connection is made. To change the S7  
value to 55 seconds, enter Command mode, then enter ATS7=55 and hit RETURN. Now, after  
dialing, the modem allows 10 more seconds for a carrier signal before aborting the call. The  
additional 10 seconds should provide enough time for international calls.  
6.2.2  
Examples of Reading Values  
To verify that you entered the value correctly in the above examples, enter ATS8? and hit RETURN  
in the first example, ATS0? in the second, and ATS2? in the third example. You should receive the  
response 005 in the first example, 030 in the second example, and 055 in the third example.  
When configuring the S-Registers, it is a good practice to include the verification read-entry in the  
same command line as the configuration assignment-entry. In the three preceding examples, enter  
ATS8=5S8?, ATS0=30S3?, and ATS7=55S7?.  
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6.3 AT Command and S-Register Summary  
The vast majority of installations are similar, with the modem being used to dial up a remote  
installation where the call is automatically answered. Your modem has a default configuration to dial  
another modem that supports error correction, data compression and flow control. If the answering  
modem is not compatible, the MultiModem can match protocols, provided the protocols are industry  
standard (i.e., ITU or Bell) and not proprietary.  
The &W command, used in conjunction with specific other AT commands and S-Registers, can re-  
configure the modem to conform to a specific application. The command AT&W0 (or AT&W) causes  
the modem to store its current parameters in its nonvolatile RAM. The command also sets the  
modem upon power up, or when it is reset with an ATZ command, the modem reads all of its  
configuration and S-Register parameters from RAM, and not from the factory settings in ROM (note  
you may recall factory installed defaults by entering AT&F8&W0). The &W command changes the  
configuration parameters stored in RAM that you specifically intend to alter. All other default  
parameters remain unchanged.  
The AT&W1 command sets the modem so that it does not store its parameters in RAM, and on  
power up or when an ATZ command is issued, parameters are read from the factory default settings  
in ROM.  
Before using the &W command, you may want to view the modem's current operating parameters.  
Use the ATL5, ATL6 and ATL7 commands to display the current modem configuration.  
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Remote Configuration  
 
MultiModemBL User Guide  
7.1 Introduction  
This chapter describes how the MultiModem’s Callback and Remote Configuration features operate.  
These features use a multilevel security system, which involves the use of LOGIN Passwords, Setup  
Passwords and Remote Escape Characters.  
The primary level security code is the modem’s LOGIN Password. Once this password is entered,  
other passwords can be used. For instance, entering the LOGIN Password will allow you to enter the  
Setup Password, which, in turn, allows you to enter Callback Passwords and dial back phone  
numbers. Callback Passwords tell your modem what dial back phone number to call.  
The Remote Escape Character is the key to using the Remote Configuration feature. The Remote  
Escape Character lets you enter Command mode via a remote call, so that you can enter AT  
commands just as if you were locally connected. You must also enter your modem’s Setup  
Password. The Remote Escape Character is contained in S-Register S13.  
7.2 Callback Feature Description  
The Callback feature protects your network from unauthorized access and helps control long  
distance costs. By use of Callback Passwords and dial back phone numbers, you can have your  
modem "dial back" remote locations immediately after being called. A special command (Enable  
Callback #DB) turns your modem into a Callback security modem. The Callback Password/Phone  
number entry is protected by two-level security (your modem's LOGIN Password and Set-Up  
Password) that keeps unauthorized personnel from changing parameters. When you first get your  
modem, you need to change both security level codes to your unique settings.  
The Callback Passwords and dial back phone numbers are in a special Callback Password/dial back  
phone number memory (30 numbers long). You use the modem's LOGIN Password and the Set-Up  
Password plus special Callback commands to access this memory. The memory is thirty numbers  
long and replaces your modem's normal phone number memory.  
Each number is 35 characters long and can contain commands as well as phone numbers. You need  
to set up your modem with the numbers and codes as part of the dial back initialization procedures.  
Your modem will also remember if the incoming call was reliable or not, and make the call back  
accordingly.  
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7.3 Remote Configuration Description  
The Remote Configuration feature is a network management tool that allows you to configure  
modems remotely. This means you could configure modems anywhere in your network from one  
location without having to visit the sites or rely on remote users to follow your instructions. With  
Remote Configuration, which is protected by two level security, you can download new parameters,  
program new V.42 capabilities and implement new features. Remote Configuration also makes  
troubleshooting a remote location a lot easier.  
The way Remote Configuration works is that S-Register S13 has been set up to contain the special  
Remote Configuration escape code. When calling a Remote Configuration equipped modem, you  
enter the proper Remote Escape code to enable entering your Set up Password. After entering it, you  
can then execute AT commands as if you were connected locally. If you set S-Register S13 to zero,  
Remote Configuration is disabled.  
7.3.1  
Initial Setup Procedures for Callback and Remote  
Configuration.  
Your modem was shipped with a default LOGIN Password and Setup Password (LOGIN=MULTI-  
TECH and Set-up=MODEMSETUP) so that you have access to the features used for configuring the  
modem. Because the defaults are in the modem owner’s manual, and anyone can find out what they  
are, you should change the codes as the first step of your initialization procedure.  
Table 7-1. Modem LOGIN, Setup and Remote Escape Code Procedures  
To change your modem’s LOGIN Password and Setup Password:  
Step  
Procedure  
Note: Passwords are upper/lower case sensitive. The case you enter here is the case that must be  
used at Log-In.  
1. Type AT#IMULTI-TECH and hit RETURN. Your modem will respond with:  
OK (if the LOGIN Password is wrong, the modem’s response is ERROR)  
2. Type AT#SMODEMSETUP and hit RETURN. Your modem will respond with the following:  
OK (or ERROR if wrong Setup Password)  
Note: At this point you can change the LOGIN Password and Setup Password.  
3. Type AT#I=xxxxxxxxxx (with any keyboard characters used, minimum 6 maximum 10) and hit  
RETURN. Your modem responds with:  
OK  
4. Type AT#S=yyyyyyyyyy (with keyboard characters used, minimum 6 maximum 10) and hit  
RETURN. Your modem responds with:  
OK  
To change your Remote Configuration feature status:  
5. If you want Remote Configuration off, set S-Register S13 to 0 (zero). Refer to Chapter 6 for  
details on how to set S-Register values.  
6. If you want Remote Configuration on and wish to change the Remote Escape Character, change  
the S-Register S13 value. If you leave it at the default value, decimal 37 (% sign) will be your  
modem’s remote escape character.  
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To turn your modem's Callback Security feature on and off:  
7. If you want Callback Security with both remote and local password security, enter AT#DB1 and  
hit RETURN. You must turn on Callback Security to be able to enter dial back phone numbers.  
8. If you want Callback Security on with just remote password security, enter AT#DB2 and hit  
RETURN. You must turn on Callback Security to be able to enter dial back phone numbers. If  
you want to use your modem to call another modem that is also set for Callback, you must enter  
AT#DB3 before you dial.  
Note: this is for your modem if you are set for #DB1 or #DB2.  
Once you have disconnected from that call, your modem will go back to its original setting.  
9. If you want Callback Security turned off, type AT#DB0 and hit RETURN.  
To set parity of the password/message prompt:  
10. The parity default value for your modem is no parity (AT#P0). If your modem's prompt messages  
use even parity, enter AT#P2 and hit RETURN. For odd parity, enter AT#P1 and hit RETURN.  
11. Enter the &W0 command and hit RETURN to store parameters and S-Register values in RAM.  
Table 7-2. Callback Password and Dial Back Phone Number Entry Procedures  
Step  
Procedure  
1. Enter your modem's LOGIN Password (as selected in Table 7-1) by entering the following:  
AT#Ixxxxxxxxxx<CR> (xxxxxxxxxx from Table 7-1)  
Enter your modem's Setup Password (as selected in Table 7-1) by entering the following:  
AT#Syyyyyyyyyy<CR>(yyyyyyyyyy from Table 7-1)  
2. Enable the Callback Security feature by entering the following:  
AT#DB2<CR> or AT#DB1<CR>  
The following message is displayed on your monitor:  
Entering Callback Mode, current phone numbers will be erased. Do you want to continue? (Y/N)  
3. Enter a Y or N and hit RETURN.  
Note: If this is your first time into Callback Mode, we recommend answering Y to clear all  
previous Callback Passwords and phone numbers from memory.  
4. Enter individual Callback Passwords for each of 30 different phone number memory locations as  
follows:  
AT#CBN0xxxxxxxxxx<CR>  
To enter Callback Password for the first location (a minimum 6 characters, up to a maximum of  
10 characters must be used).  
AT#CBN1xxxxxxxxxx<CR>  
To enter Callback Password for the second location...etc (a minimum 6 characters, up to a  
maximum of 10 characters must be used).  
Note: The first character of your first Callback Password must be non-numeric.  
5. Enter individual phone numbers for each of the 30 memory locations as follows:  
AT+ - DP...????N0 <CR> (number for location N0)  
AT+ - DT...????N1 <CR> (number for location N1)...etc  
Note: You must indicate within the command string that the modem either Pulse dial (ATDP...) or  
Tone dial ATDT...).  
The maximum length of the number is 35 characters. The number may include commands as  
well as your number, so as to create macro-type command numbers.  
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The + and/or - characters entered before the phone number are optional. The + (Deposit  
Number) code allows a caller to enter the number he or she wishes the Callback modem to call  
back when the caller uses a particular password (Step 3 of Table 7-3). The - character enables  
direct entry when the caller uses that correct password (Step 3 of Table 7-3) without the Callback  
modem having to return the call.  
The ??? entry at the end of the phone number is optional and indicates a subcode number to the  
main phone number for that location. The ??? used to dial different extensions at the same basic  
number. To use this optional feature, enter the number of ? marks where indicated equal to the  
number of digits in the desired extension number, (i.e., with a 4 digit extension enter ????). When  
a caller uses that particular password (Step 3 of Table 7-3), he or she then enters an extension  
number directly after the password, with the same number of digits as the number of ? marks  
originally entered. When calling back that particular number, your modem will also dial the  
indicated extension number.  
Note: To view Callback Passwords/Numbers, use the L Command.  
6. To store changed parameters to memory, enter AT&W0 and hit RETURN.  
Note: If you have enabled Callback Security (#DB1 in step 2 of Table 7-2), the modem will be  
secured locally. To gain local access, you must again perform steps 7 and 8.  
7. Enter your modem's LOGIN Password (as selected in Table 7-1) by entering:  
AT#Ixxxxxxxxxx<CR> (xxxxxxxxxx from Table 7-1)  
8. Enter your modem's Setup Password (as selected in Table 7-1) by entering:  
AT#Syyyyyyyyyy<CR> (yyyyyyyyyy from Table 7-1)  
Table 7-3. Callback Operational Sequence Procedures  
Perform the following steps when dialing into a dialback modem:  
Step  
Procedure  
1. When called, the modem answers and after a slight delay, responds with:  
Password>  
2. Enter your modem's LOGIN Password (Table 7-1) and hit RETURN. If entered correctly, the  
modem responds with:  
DB>  
3. Enter the Callback Password corresponding to the phone number you wish called back and hit  
RETURN (Callback Passwords and phone numbers entered in Table 7-2). You can also use  
special characters + and -. They must have been entered as part of the Callback phone numbers  
in Step 5 of Table 7-2. If you use the - character along with your password, the Callback modem  
will connect directly without hanging-up and calling back. If you use the + character along with  
your password, you can also enter a phone number which you wish the Callback modem to dial  
after hanging-up. The + and - characters must be entered after the Dial-back password, (i.e.,  
DB>xxxxxx+). This is also the point where you enter an extension number if your Callback  
number used the ??? feature (Step 5 in Table 7-2).  
You have three tries at each prompt to enter the information properly, with an incorrect entry  
resulting in a password retry. You must enter the requested information correctly within one  
minute or the Callback modem will hang-up. When the information is entered properly, the called  
modem will hang-up and after a 15 second delay, call you back. When your modem answers, the  
dialback modem will respond with the following:  
Password>  
4. Enter the modem's LOGIN Password again (the same as in Step 1). The Callback modem  
responds with:  
CONNECT  
You are now in Data Mode.  
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7.3.2  
Remote Configuration Procedures  
The procedures for using the Remote Configuration features are the same whether or not a call  
originates from the remote modem. Once the modem is on-line, perform the procedures in Table 7-4.  
Table 7-4 Remote Configuration Operation Procedures  
Step  
Procedure  
1. Remote Escape Configuration requires %%%AT<CR> to be sent if the default value in S-  
Register S13 has not been changed.  
The modem responds with:  
1. - DATA Mode  
2. - COMMAND Mode  
2. You then select 1 or 2. With 1, the modem goes back into data mode and with 2, the modem  
responds with the following:  
Password>  
3. Enter your Setup Password, and if the code is correct the modem responds with:  
OK  
You can now use any AT commands of the modem being remotely configured as if they were  
being entered locally. You cannot change the setup of the LOGIN Password until you enter the  
proper LOGIN Password.  
4. When you are done entering AT commands and you want to exit, type AT0 and hit RETURN.  
The modem responds with:  
1. DATA Mode  
2. COMMAND Mode  
5. Enter a 1 to go back on-line with your computer, or enter 2 and the correct password to talk to  
your modem.  
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7.4 Remote Configuration and Callback Security AT Commands  
The following AT commands are used with Remote Configuration and Callback Security features.  
Assign Passwords for Callback Phone Numbers #CBN  
When you have callback security enabled for the modem, anyone trying to connect with the modem  
will be required to furnish a password. The #CBN command allows you to enter passwords for each  
of the 30 memory locations used for callback security. The length of each password can be up to 10  
characters, but must be at least 6 characters. Any ASCII character can be used.  
The format for this command is AT#CBNyyxxxxxxxx<CR> with xxxxxxxx representing the  
password and yy being the memory location (0-29). Each callback password (xxxxxxxx) must start  
with a non-numeric character.  
Callback Security Enable/Disable  
#DB  
The purpose of this command is to enable or disable (default setting) your modem's callback security  
option. Once this command is executed, you modem will undergo some significant changes. For  
example, the phone number memory locations (N0 through N9) will be used for passwords and  
phone numbers. In other words, you will not be able to dial from memory or use the DTR dialing  
feature.  
You can turn on callback security by typing AT#DB1 or AT#DB2 and pressing <CR>. If you want to  
engage both remote and local password security, use the #DB1 command. This sets up the modem  
so you have to provide passwords to dial into the modem and to dial out. For remote password  
security only, use the #DB2 command. This allows the local operator to dial out without providing the  
LOGIN and SETUP passwords. Use #DB3 when calling another modem with callback security active.  
Change LOGIN Password  
#I  
The default LOGIN password for your modem is "MULTI-TECH". If you choose to activate callback  
security, you should change the LOGIN password using this command in the following format:  
AT#Ixxxxxxxxxx<CR> (where xxxxxxxxxxxxxxxx is the current LOGIN password). Your modem will  
respond with "OK", indicating that you can enter the new LOGIN password as follows:  
AT#I=yyyyyyyyyy<CR>  
You can select any combination of keyboard characters (upper/lower case sensitive) between six  
and ten characters long.  
Change SETUP Password  
#S  
The default SETUP password for your modem is "SMODEMSETUP". If you choose to activate  
callback security, you should change the SETUP password using this command in the following  
format:  
AT#Stttttttttt<CR> (where tttttttttt is the current SETUP password). Your modem will respond with  
"OK", indicating that you can enter the new SETUP password as follows:  
AT#s=uuuuuuuuuu<CR>  
You can select any combination of keyboard characters (upper/lower case sensitive) between six  
and ten characters long.  
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Erase Callback Password  
#RCBNxx  
This command erases the single callback password specified by xx (0 through 29).  
Erase Callback Phone Number #RDNxx  
This command erases the single phone number specified by xx (0 through 29).  
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7.5 Remote Configuration/Callback Security S-Registers  
The following S-Registers are used with Remote Configuration and Callback Security features.  
Remote Configuration Character (S13)  
S13 defines the modem’s remote configuration escape character. When the S13 character is entered  
three consecutive times from a remotely connected site, your modem responds to it with its Remote  
Configuration procedure.  
Units:  
ASCII  
Range:  
Default:  
0-127  
37 (% sign)  
Callback Time Delay (S15)  
S15 defines the time delay for Callback attempts after initial passwords have been exchanged  
between modems.  
Unit:  
Range:  
Default:  
Seconds  
10-255  
20  
Callback Attempts (S16)  
S16 defines the number of Callback attempts after initial passwords have been exchanged between  
modems.  
Unit:  
Range:  
Default:  
1 Attempt  
1-255  
4
Failed Password Attempts (S26)  
S26 counts the number of times there has been a failed password attempt. For example, if you  
entered ATS26? the message 003 would be displayed, meaning someone has failed three times to  
gain access to your modem using its password security system.  
Units:  
1 failed attempt  
Range:  
Default:  
0-255  
0
Local Inactivity Timer (S29)  
S29 defines the amount of idle time that can elapse between AT commands after the SETUP  
password has been entered. If this timer expires, the LOGIN and SETUP passwords will have to be  
re-entered.  
S29 only takes effect when the modem has been sent a #DB1 command, which secures the modem  
from local and remote configuration or dialing (i.e., no AT commands can be sent until the LOGIN  
and SETUP passwords have been entered).  
Units:  
Range:  
Default:  
Minutes  
1-255  
20  
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MultiModemBL User Guide  
8.1 Introduction  
Each time you power up the MultiModem, it performs an automatic self- test to ensure proper  
operation. The modem also has four diagnostic test features: Local Analog Loopback, Digital  
Loopback (remote/automatic), Digital Loopback (local/manual) and a modem Back-to-Back test.  
A loopback test involves entering data from your PC and looping that data through the circuits of your  
modem and/or a remote modem. When the loop has been completed, the original data entered  
should match the data received back on your PCs monitor after the test.  
The Local Analog Loopback Test allows you to verify that the modem’s transmitter and receiver  
circuits are functioning properly.  
The Digital Loopback Test (local/manual) allows you to verify that the remote computer or terminal,  
the remote modem, serial ports, the telephone line and the local modem are functioning properly.  
The Digital Loopback Test (remote/automatic) allows you to verify that the local computer or terminal,  
the two modems and the transmission line between them are functioning properly.  
The Back-to-Back test lets you connect two MultiModems with a back-to-back cable to verify proper  
modem operation.  
In asynchronous mode, upon completion of testing, enter either Escape Sequence, +++AT<CR> or  
<BREAK>AT<CR>.  
Note: All loopback tests will operate at all speeds except 300 bps. Disable error correction  
(&E0&W0<CR>) before engaging in loopback tests (self-test and back-to-back test not affected).  
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8.2 Local Analog Loopback Test/V.54 Loop 3  
In this test, data from your computer or terminal is sent to your modem's transmitter, converted into  
analog form, looped back to the receiver, converted into digital form and then received back at your  
monitor for verification. No connection to the phone line is required. See Figure 8-1.  
UUUUU  
UUUUU  
Digital Analog  
Computer or Terminal  
Local MultiModem  
Figure 8-1. Local Analog Loopback Test  
The test procedure is as follows:  
1. Connect the modem to your computer. With your communication software, set the desired baud  
rate.  
2. Type ATU0 (or ATU) and hit ENTER. This places your modem in Analog Loopback mode, in the  
Originate mode. The modem is now out of the Command mode and in a pseudo On-Line mode.  
3. Once you receive a connect message (if responses are enabled), enter data from your keyboard.  
For this test, typing multiple upper case "U" characters is a good way to send an alternating test  
pattern of ones and zeros.  
4. For a more complete test, you should also test the modem in Answer mode. To do this, you must  
“escape” from Originate mode by entering an Escape Sequence (+++AT<CR> or  
<BREAK>AT<CR>) . Then type ATU1 and hit ENTER to place the modem in Analog Loopback  
mode, in the Answer mode. Then repeat step 3.  
5. When testing is completed, you may exit Answer mode by entering an Escape Sequence  
(+++AT<CR> or <BREAK>AT<CR>), which returns the modem to Command mode.  
6. Your modem passes this test if the data entered from your keyboard is the same as the data  
received on your monitor. If different data is appearing on your monitor, your modem is probably  
causing the problem, although it could also be your computer. If your modem passes this test,  
but you are receiving errors while On-line, the remote modem or the phone line could be at fault.  
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8.3 Digital Loopback Test/V.54 Loop 2 (Local/Manual)  
In this test, your modem must be On-Line with another modem that can respond to a request for  
Digital Loopback, such as another MultiModem. The Digital Loopback Test is an on-line test that  
loops data sent from one modem across the phone line to another modem, then back to the first  
modem. See Figure 8-2.  
There are two ways to put a modem into Digital Loopback mode.  
1. Locally or Manually, described here in section 8.3.  
2. Remotely or Automatically, see section 8.4.  
Note: The Digital Loopback Tests can only be used with the modem in Normal mode (error  
correction off).  
ATU3  
UUUUU  
UUUUU  
Digital Analog  
Analog Digital  
Computer or Terminal Local MultiModem  
Remote MultiModem Computer or Terminal  
Figure 8-2. Digital Loopback Test (local/manual)  
In this test the local modem is placed in Digital Loopback mode. Data is entered and transmitted from  
the remote modem (which is not in digital loopback mode), sent across the phone line to the local  
modem and looped back to the remote modem.  
The test procedure is as follows:  
1. Go into Terminal mode. Type AT and hit ENTER; you should get an OK message.  
2. Dial the remote modem by entering the Dial command and the phone number, to establish On-  
line mode.  
3. Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into  
Command mode, while still maintaining the pseudo On-line mode with the remote modem.  
4. Type ATU3 from the local PC and hit ENTER. Once you receive an OK message from your  
modem (if responses are enabled), the local modem is placed in Digital Loopback mode.  
5. Data is typed from the remote keyboard. For this test, typing multiple upper case "U" characters  
is a good way to send an alternating test pattern of ones and zeros. The data received by the  
local modem will enter its analog receiver, be converted to digital data, be reconverted into  
analog, and then looped through its transmitter back to the remote modem. Your modem passes  
this test if the data entered from the remote keyboard is the same as the data received on the  
remote monitor.  
6. When testing is complete, you may end the test by typing an Escape Sequence (+++AT<CR> or  
<BREAK>AT<CR>) to bring your modem into Command mode. The modem should respond  
with an OK message. If you wish to stay On-line with the remote modem for normal data  
transmission, type AT0 and hit ENTER. If you wish to terminate the call, type ATH and hit  
ENTER to hang up.  
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Chapter 8 - Modem Testing  
8.4 Digital Loopback Test/V.54 Loop 2 (Remote/Automatic)  
In this test, your modem must be On-line with another modem set up to respond to a request for  
Digital Loopback, such as another MultiModem. With the MultiModem, this ability to respond is  
controlled by the &T command. AT&T4 enables the response to Digital Loopback Test (remote/  
automatic). AT&T5 disables the response. The modem defaults to disable on power up, so this must  
be changed on the remote modem before the modem will respond to a request for the Digital  
Loopback Test (remote/automatic).  
Initiate the Digital Loopback Test (remote/automatic) with the ATU2 command which automatically  
places the remote modem in digital loopback mode. Data from your computer or terminal are  
transmitted through your modem, and over the phone line to the remote modem, where they are then  
looped back to your modem. See Figure 8-3.  
The test procedure is as follows:  
1. Go into Terminal mode. Type AT and hit ENTER; you should get an OK message.  
2. Dial the remote modem by entering the Dial command and the phone number, to establish On-  
line mode.  
Note: The &T4 command must be set on the remote modem to run this test.  
UUUUU  
UUUUU  
Digital Analog  
Analog Digital  
Computer or Terminal Local MultiModem  
Remote MultiModem Computer or Terminal  
Figure 8-3. Digital Loopback Test (remote/automatic)  
3. Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into  
Command mode, while still maintaining the connection with the remote modem.  
4. Type ATU2 and hit ENTER. The local modem responds to this command by transmitting an  
unscrambled marking signal, which causes the remote modem to place itself in Digital Loopback  
mode. Then the local modem exits Command mode and enters pseudo On-line mode.  
5. Type data from your keyboard. For this test, typing multiple upper case "U" characters is a good  
way to send an alternating test pattern of ones and zeros. The data received by the remote  
modem will enter its analog receiver, be converted to digital data, be reconverted into analog,  
and then looped through its transmitter back to the local modem. Your modem passes this test if  
the data entered from the local keyboard is the same as the data received on your monitor.  
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MultiModemBL User Guide  
8.5 Back-to-Back Test  
This test lets you connect two MultiModems with an RJ-11 cable to verify proper operation. Using a  
modem that is known to be operational, you can test a second modem that is suspect.  
1. Plug the modular ends of an RJ-11 cable into both MultiModem’s LEASE jack connectors.  
2. Force DTR ON in both local and remote modems (Switch #1 DOWN).  
3. Enter the command AT$SB9600$BA0&W0<CR> on both local and remote modems. This sets  
the serial speed to 9600bps. Make sure that the terminal/computer is set for 9600 bps.  
4. Set both modems in Leased-Line mode (DIP-Switch # 10 DOWN).  
5. Set one modem to Answer enabled (DIP-Switch #5 UP) and the other modem to Originate  
enabled (DIP-Switch #5 DOWN). Note it does not matter which modem (local/remote) is set to  
Answer/Originate—just so they are set opposite.  
6. Set DIP-Switch # 3 UP on both local and remote modems. This changes the transmit level to  
-15dB and this change is necessary to operate in back-to-back mode  
7. Turn on both units and wait for carrier detect (CD).  
8. Short out pins 2 and 3 on the RS-232C interface on the remote modem (i.e.., with a paper clip or  
some other metal device).  
Remote Site: Short Pins #2 and  
#3 on the RS-232 Interface  
PHONE  
PSTN  
LEASE  
EIA RS232C  
ON  
OFF  
VOLUME  
POWER  
PHONE  
PSTN  
LEASE  
EIA RS232C  
ON  
OFF  
VOLUME  
POWER  
Figure 8-4A. Back-to-Back Test Cabling  
9. Entered characters should echo back to the sending modem.  
Back-to-Back  
Cable  
Remote Modem  
in Loopback Mode  
Local  
Modem  
Figure 8-4B. Back-to-Back Testing  
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Chapter 8 - Modem Testing  
8.6 Synchronous Mode Testing  
The following tests must be run with your modem in Synchronous mode (DIP Switch #12 in the Up  
(OPEN) position), DIP Switch #9 controls the modem’s Synchronous mode testing function. (Refer to  
Chapter 9 for DIP Switch information.) The test procedures for Synchronous mode are different from  
those for Asynchronous mode. In Synchronous mode, you cannot access the modem’s AT  
commands.  
With DIP Switch #9, you can perform either the Digital Loopback Test (remote/automatic) or the  
Digital Loopback Test (local/manual) in Synchronous mode, as described in the following sections.  
There is also a Local Analog Loopback Test, documented in section 8.7.  
8.7 Local Analog Loopback Test (Synchronous Mode)  
This test diagnoses the connection between your modem and your computer or terminal. In Local  
Analog Loopback Test mode, data entered at the local computer or terminal are sent through the  
local modem’s transmit and receive circuits (much like entering an ATU or ATU1 command in  
Asynchronous mode). You then compare the test characters (multiple upper case “U” characters in  
Figure 8-5) on your monitor with the characters you typed. If the characters don’t match, check your  
computer’s COM port setting, then verify your communication software’s configuration.  
To initiate the Local Analog Loopback Test, with the modem in Synchronous mode:  
1. Enter AT&M1U. This first switches your modem form asynchronous to synchronous mode, and  
places it into the Analog Loopback/Originate mode. The modem is now out of the Command  
mode and in the pseudo On-Line mode.  
2. Once you receive a connect message (if responses are enabled), enter data from your keyboard.  
For this test, typing multiple upper case "U" characters is a good way to send an alternating test  
pattern of ones and zeros.  
3. For a more complete test, you should also test the modem in Answer mode. To do this, Type the  
Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into  
Command mode, while still maintaining the connection. Then type AT&M1U1 and hit ENTER to  
place the modem in Analog Loopback mode, in the Answer mode. Then repeat step 2.  
UUUUU  
UUUUU  
Digital Analog  
Computer or Terminal  
Local MultiModem  
Figure 8-5. Synchronous Mode Local Analog Loopback Test  
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8.8 Digital Loopback Test (Local/Manual) (Synchronous Mode)  
This test must be run when you have a data connection with another modem. If a Local Analog  
Loopback Test resulted in errors, and this test passes without errors, then the problem exists in your  
computer-to-modem connection. In Digital Loopback Test (local/manual) mode, data passed from the  
remote modem’s transmit circuit are looped back from the local modem and are received at the  
remote modem’s receive circuit (multiple upper case “U” characters in Figure 8-6).  
First make certain that you are set up for Synchronous operation by placing DIP-Switch #12 in the  
UP position. To initiate the Digital Loopback Test (local/manual), DIP-Switch #9 must be in the UP  
position, and the Answer/Originate switch (front of the modem) must be toggled to the UP position.  
Once you receive an OK message from your modem (if responses are enabled), the local modem is  
placed in Digital Loopback mode.  
To exit the Digital Loopback Test (local/manual), toggle the Answ/Orig switch to the Answer position.  
UUUUU  
UUUUU  
Digital Analog  
Analog Digital  
Computer or Terminal Local MultiModem  
DIP-Switch #9  
Remote MultiModem Computer or Terminal  
UP; Answ/Orig  
Switch Toggled to  
Answ position  
when On-line  
Figure 8-6. Synchronous Mode Digital Loopback Test (local/manual)  
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Chapter 8 - Modem Testing  
8.9 Digital Loopback Test (Remote/Automatic) (Synchronous Mode)  
This test must be run when you have a data connection with another modem. In this test, data is  
passed to the remote modem and is looped back to the local modem (as if an ATU2 command was  
issued in Asynchronous test mode), as shown in Figure 8-7. This lets you test the local and remote  
modem’s transmit and receive circuits, as well as your computer’s serial COM port and the phone  
lines. If the test results in a mismatch of entered/received data (multiple upper case “U” characters in  
Figure 8-6), the Local Analog Loopback Test should be performed on both the remote and local  
modems. If that test is successful, the problem may be the phone lines.  
First make certain that you are set up for Synchronous operation by placing DIP-Switch #12 in the  
UP position. To initiate the Digital Loopback Test (remote/automatic), DIP-Switch #9 must be in the  
DOWN position, and the Answer/Originate switch (front of the modem) must be toggled to the UP  
position. Once you receive an OK message from your modem (if responses are enabled), the local  
modem is placed in Digital Loopback mode. To exit the Digital Loopback Test (remote/automatic),  
toggle the front panel Answ/Orig switch to the Answer position.  
UUUUU  
UUUUU  
Digital Analog  
Analog Digital  
Computer or Terminal Local MultiModem  
DIP-Switch #9  
Remote MultiModem Computer or Terminal  
UP; Answ/Orig  
Switch Toggled to  
Answ position  
when On-line  
Figure 8-7. Synchronous Mode Digital Loopback Test (remote/automatic)  
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106  
 
Chapter 9 - DIP-Switch Settings  
 
MultiModemBL User Guide  
9.1 Introduction  
There are several DIP-Switch options on the modem’s printed circuit (PC) board. The DIP-Switches  
are accessible through a cut-out on the side of the modem. This chapter explains the modem’s  
printed-circuit board options. Sixteen DIP-Switch settings and the modem's speaker volume control  
are explained in detail, including all default settings.  
Power Switch  
Power Jack  
LED  
Indicators  
RS-232/V.24  
Connector  
Lease-Line  
Jack  
Dial-up Jack  
Phone Jack  
OPEN  
OPEN  
1
2
3
4
5
6
7
8
9
10 11 12  
13 14 15 16  
16-position DIP-switches  
Figure 9-1. PC Board (BL models)  
Note: There is no Phone connector on BLK models  
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Chapter 9 - DIP-Switch Settings  
9.2 DIP-Switch Option Settings  
Switch #1  
Forced DTR -- "DTR"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The modem must have a high DTR signal in order to operate. DTR is provided to the modem by the  
terminal or computer to which it is attached, through pin 20 of the RS-232C/V.24 interface. If your  
terminal or computer is not providing DTR to the modem, you can force the DTR signal high with DIP-  
Switch #1.  
DTR function normally =  
DTR forced On  
Factory Default Setting =  
Switch #1 UP  
Switch #1 DOWN  
UP  
=
Switch #2  
Flow Control - &E4/&E5  
(Asynchronous Mode/Leased Line/Dial-Up)  
With Hardware Flow Control, the modem uses its RS-232C/V.24 interface to control the flow of data  
from the computer or terminal to which it is attached. The CTS signal on Pin 5 of the RS-232C/V.24  
is brought low to stop the flow of data, and is brought high to restart it. Place DIP-Switch #2 in the UP  
position to enable Hardware Flow Control (&E4). Xon/Xoff Flow Control (&E5) is another flow control  
method. Xon/Xoff characters in the data dictate the start and stop of data flow from the computer or  
terminal. Place DIP-Switch #2 in the DOWN position to select Xon/Xoff Flow Control.  
Hardware Flow Control (&E4)  
Xon/Xoff Flow Control (&E5)  
Factory Default Setting  
=
=
=
Switch #2 UP  
Switch #2 DOWN  
UP  
Switch #2  
SDLC/BSC Option  
(Synchronous Mode/Leased Line/Dial-Up)  
Synchronous Data Link Control (SDLC) and Binary Synchronous Control (BSC) are two error  
correction protocols used in the IBM Mainframe environment. Place DIP-Switch #2 in the UP position  
to enable SDLC mode, and place DIP-Switch #2 in the DOWN position to enable BSC mode.  
SDLC Mode  
BSC Mode  
Factory Default Setting =  
=
=
Switch #2 UP  
Switch #2 DOWN  
UP  
Switch #3  
Enable/Suppress Responses -- "Q"  
(Asynchronous Mode/Dial-Up)  
In some Asynchronous mode applications, you may want to suppress all responses from the modem.  
Place DIP-Switch #3 in the DOWN position to enable Result Code responses (Q0). Place DIP-Switch  
#3 in the UP position, and answer mode is handled without responses and echo turned off (Q2), but  
originate is still intelligent.  
Enable Responses: Originate/Answer (Q0)  
Suppress Responses: Answer (Q2)  
Factory Default Setting  
=
=
=
Switch #3 DOWN  
Switch #3 UP  
DOWN  
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MultiModemBL User Guide  
*Switch #3  
dB Transmission Levels  
(Asynchronous/Synchronous Mode/Leased Line)  
2834 Series:  
DIP-Switch #3 adjusts dB transmission levels required by some phone carriers. Place DIP-Switch #3  
in the DOWN position to enable -9 dB transmission. Place DIP-Switch #3 in the UP position to enable  
-15 dB transmission.  
-9dB Transmission  
-15dB Transmission  
Factory Default Setting =  
=
=
Switch #3 DOWN  
Switch #3 UP  
DOWN  
1932 and 1432 Series:  
DIP-Switch #3 adjusts dB transmission levels required by some phone carriers. Place DIP-Switch #3  
in the DOWN position to enable 0 dB transmission. Place DIP-Switch #3 in the UP position to enable  
-10 dB transmission.  
0dB Transmission  
-10dB Transmission  
Factory Default Setting =  
=
=
Switch #3 DOWN  
Switch #3 UP  
DOWN  
*This Switch is not applicable to BLK models.  
Switch #4  
AS/400 Mode  
(Synchronous Mode/Leased Line/Dial-UP)  
The modem can function in the IBM AS/400 environment (appearing like an IBM5853 modem). First,  
DIP-Switch #7 must be placed in the UP position. This establishes an RTS/CTS condition (state  
typical for an IBM5853 modem in half-duplex mode). Next, place DIP-Switch #4 in the DOWN  
position. This "spoofs" the modem into operating like an IBM5853 modem in AS/400 applications.  
DIP-Switch #4 in the UP position disables this function. Note that the modem must be in Command  
mode to allow AS/400 mode (DIP-Switch #8 DOWN); and in Synchronous mode (DIP-Switch #12  
UP).  
AS/400 Mode Enabled =  
AS/400 Mode Disabled =  
Factory Default Setting =  
Switch #4 DOWN  
Switch #4 UP  
UP  
Switch #4  
Unix UUCP Spoofing  
(Asynchronous Mode/Leased Line/Dial-Up)  
The modem can be configured for use with Unix equipment which employs ACK flow control to  
monitor data integrity. The modem can do "UUCP spoofing", where the modem is able to generate  
ACKs at the DTE interface. Data then is transmitted more time-efficiently, because the delay of  
waiting for data to be received then waiting for the ACK to be returned at the remote end, is  
eliminated. Placing DIP-Switch #4 in the DOWN position enables UUCP spoofing.  
UUCP Spoofing Enabled  
UUCP Spoofing Disabled  
Factory Default Setting  
=
=
=
Switch #4 DOWN  
Switch #4 UP  
UP  
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Chapter 9 - DIP-Switch Settings  
Switch #5  
Enable/Disable Auto-Answer - "Ans"  
(Asynchronous Mode/Synchronous Mode/Dial-Up)  
In some originate-only applications, you may wish to disable the modem’s automatic answering  
capabilities. This may be true if you have a telephone set attached to a modem and wish to receive  
voice calls that you yourself would answer instead of the modem. Place DIP-Switch #5 in the UP  
position to enable Auto-Answer. Place DIP-Switch #5 in the DOWN position to disable Auto-Answer.  
Auto-Answer Enabled  
Auto-Answer Disabled  
(Factory Default Setting  
=
=
=
Switch #5 UP  
Switch #5 DOWN  
UP)  
Switch #5  
Originate/Answer Mode  
(Asynchronous/Synchronous Mode/Leased Line)  
The modem functions in either Originate mode or Answer mode. Place DIP-Switch #5 in the DOWN  
position to enable Originate mode. Place DIP-Switch #5 in the UP position to enable Answer mode.  
Originate Mode Enabled  
Answer Mode Enabled  
(Factory Default Setting  
=
=
=
Switch #5 DOWN  
Switch #5 UP  
UP)  
Switch #6  
Maximum Throughput Setting  
(Asynchronous Mode/Leased Line/Dial-Up)  
Some applications require you to dial into services with maximum throughput on, and other  
applications where maximum throughput must be off (i.e., service not supporting error correction, or  
the V.42 handshake interferes with logon sequence). DIP-Switch #6 is used for switching between  
these two modes. This DIP-Switch controls three important parameters (error correction, speed  
conversion and serial port speed), which in effect enables or disables maximum throughput.  
Maximum Throughput Enabled =  
Maximum Throughput Disabled =  
Switch #6 UP  
Switch #6 DOWN  
UP  
Factory Default Setting  
=
Switch #6  
Slave Clocking  
(Synchronous Mode/Leased Line/Dial-Up)  
In Synchronous mode, DIP-Switch #6 controls the option of having timing controlled by the receive  
clock. The originate modem, in effect, adjusts to the answer (remote) modem. Place DIP-Switch #6 in  
the DOWN position to enable Slave Clocking. Place DIP-Switch #6 in the UP position to disable  
Slave Clocking.  
Slave Clocking Enabled  
Slave Clocking Disabled  
Factory Default Setting  
=
=
=
Switch #6 DOWN  
Switch #6 UP  
UP  
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MultiModemBL User Guide  
Switch #7  
Request To Send Forced - "RTS"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
If your computer or terminal uses RTS-CTS protocol (typically used in some synchronous  
applications, but also if using hardware pacing for V.42 error correction or speed conversion), you  
may want to set RTS to function independently of CTS (DIP-Switch #7 UP). For most applications,  
especially asynchronous, this switch should be set so that RTS is forced On (DIP-Switch #7 DOWN)  
RTS functions Normally  
RTS forced On  
Factory Default Setting  
=
=
=
Switch #7 UP  
Switch #7 DOWN  
DOWN  
Switch #8  
Enable/Disable Command Mode -- "Com"  
(Asynchronous/Synchronous Mode/Leased/Dial-Up)  
In some applications you may want to disable the modem's Command mode so that the modem does  
not recognize or react to AT or V.25bis commands. This may be true in strictly auto-answer  
applications where no call origination is required. Place DIP-Switch #8 in the DOWN position to  
enable Command mode. Place DIP-Switch #8 in the UP position to disable Command mode. The  
factory default setting is Command mode enabled.  
Disable Command Mode  
Enable Command Mode  
Factory Default Setting  
=
=
=
Switch #8 UP  
Switch #8 DOWN  
DOWN  
Switch #9  
Digital Loopback Test  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
When in Synchronous mode, this switch controls both Local Digital Loop and Remote Digital Loop  
tests while on-line. When the Voice/Data switch is toggled to the Answer mode position (UP) and  
DIP-Switch #9 is in the UP position, the modem performs the Local Digital Loopback test. When DIP-  
Switch #9 is DOWN and the Voice/Data switch is toggled to Answer mode position (UP), the modem  
performs the Remote Digital Loopback test.  
Local Digital Loopback Test  
Remote Digital Loopback Test =  
Factory Default Setting  
=
Switch #9 UP  
Switch #9 DOWN  
DOWN  
=
Switch #10  
Leased Line/Dial-Up Operation -- "DDD"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The modem operates in either leased-line or dial-up modes. This switch controls leased-line/dial-up  
operation. Place DIP-Switch #10 in the UP position for Dial-Up operation. Place DIP-Switch #10 in  
the DOWN position for Leased-Line operation  
Dial-Up Operation  
Leased Line Operation  
Factory Default Setting  
=
=
=
Switch #10 UP  
Switch #10 DOWN  
UP  
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Chapter 9 - DIP-Switch Settings  
Switch #11  
"AT" Responses/Multi-Tech Responses  
(Asynchronous Mode/Leased line/Dial-Up)  
In Asynchronous mode, you can set the modem to respond with Result Codes according to the  
"Multi-Tech" command response set (Switch #11 in the DOWN position), or to "AT" command  
response set (Switch #11 in the UP position). The &Q command performs the same function  
(choosing AT or Multi-Tech Result Codes), and is explained further in Section 5.3 of this manual.  
"AT" Responses (&Q1)  
"Multi-Tech" Responses (&Q0  
Factory Default Setting  
=
=
=
Switch #11 UP  
Switch #11 DOWN  
DOWN  
Switch #11  
Internal/External Clocking  
(Synchronous Mode/Leased Line/Dial-Up)  
In Synchronous mode, the transmit clock can be supplied by the DTE on pin 24 of the RS-232C/V.24  
interface by placing DIP-Switch #11 UP. Place DIP-Switch #11 in the DOWN position to enable DCE  
to control clocking (internal clock via pins 15 and 17 of the RS-232/V.24 interface).  
External Clock (pin 24)  
Internal Clock (pins 15/17)  
Factory Default Setting  
=
=
=
Switch #11 UP  
Switch #11 DOWN  
DOWN  
Switch #12  
Asynchronous/Synchronous Operation -- "Sync"  
(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)  
The modem can operate in either Asynchronous mode or Synchronous mode. In Synchronous mode,  
start and stop bits are eliminated. The modem's internal clock circuits on the RS-232C/V.24 pins 15  
and 17 are activated. The modem's Command mode is not accessible in Synchronous mode. This  
switch is a means to alternate and to access either mode. In Synchronous mode, you may want to  
set the RTS forcing and CTS forcing DIP-Switches so that both of signals act normally (not forced  
on).  
Synchronous Operation  
Asynchronous Operation  
Factory Default Setting  
=
=
=
Switch #12 UP  
Switch #12 DOWN  
DOWN  
Switches #13 and #14  
Speed Switches  
(Synchronous Mode/Leased Line)  
DIP-Switches #13 and #14 are used to set the modem’s data transmission rate. Switches #13 and  
#14 are used in combination, typically in leased-line and call origination applications.  
Note: The modem baud rate command ($MBn) overrides the setting of these speed selection  
switches (DIP switches #13 and #14).  
2834 Series:  
28800 bps Operation  
19200 bps Operation  
14400 bps Operation  
9600 bps Operation  
=
=
=
=
Switch #13 UP and Switch #14 UP  
Switch #13 DN and Switch #14 UP  
Switch #13 UP and Switch #14 DN  
Switch #13 DN and Switch #14 DN  
Factory Default Setting =  
Switch #13 UP and Switch #14 UP  
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MultiModemBL User Guide  
1932 Series:  
19200 bps Operation  
14400 bps Operation  
9600 bps Operation  
2400 bps Operation  
=
=
=
=
Switch #13 UP and Switch #14 UP  
Switch #13 DN and Switch #14 UP  
Switch #13 UP and Switch #14 DN  
Switch #13 DN and Switch #14 DN  
Factory Default Setting =  
Switch #13 UP and Switch #14 UP  
1432 Series:  
14400 bps Operation  
9600 bps Operation  
4800 bps Operation  
2400 bps Operation  
=
=
=
=
Switch #13 UP and Switch #14 UP  
Switch #13 DN and Switch #14 UP  
Switch #13 UP and Switch #14 DN  
Switch #13 DN and Switch #14 DN  
Factory Default Setting =  
Switch #13 UP and Switch #14 UP  
Switch #15  
Carrier Detect/DSR Forcing -- "DSR"  
(Asynchronous/Synchronous Mode/Dial-Up/Leased Line)  
Some terminals react in unusual ways to the toggling of the Carrier Detect (CD - RS-232C/V.24 pin  
6) signals. The most common symptom is that the modem does not respond to commands, or does  
not echo characters. In these cases, it is advisable to force these two signals On in order for the  
terminal to communicate properly with the modem in Command mode. This is done by setting DIP-  
Switch #15 DOWN. With DIP-Switch #15 in the UP position, both CD and DSR will be either on or off,  
depending on the On-Line status.  
CD and DSR normal  
CD and DSR forced On  
Factory Default Setting  
=
=
=
Switch #15 UP  
Switch #15 DOWN  
UP  
Switch #16  
2 Wire/4 Wire Operation  
(Asynchronous/Synchronous Mode)  
The modem works over either 2-wire or 4-wire leased lines. To select 4-wire operation, place Switch  
#16 DOWN (Default); and to select 2-wire operation, place Switch #16 UP.  
2-Wire Leased Line  
4-Wire Leased Line  
Factory Default Setting  
=
=
=
Switch #16 UP  
Switch #16 DOWN  
DOWN  
9.3 Speaker Volume Control  
You can adjust the volume of the modem’s phone-line monitor speaker with a volume control knob,  
located on the back of the modem next to the RS-232C connector (see Figure 9-1 for location). Turn  
the knob clockwise to increase the modem's volume and counterclockwise to decrease speaker  
volume. See Speaker Control Command (M) in Section 5.4.6.  
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Chapter 9 - DIP-Switch Settings  
9.4 Recording Option Configurations  
This section lets you record any changes you may have made to the DIP-Switch settings. Circle the  
appropriate setting and record the effect for future reference.  
DIP-Switches  
Switch  
Function  
Position  
Effect  
#1  
Force DTR/DTR from Interface*  
UP*  
DOWN  
#2  
Flow Control &E4*/&E5  
UP*  
(Async/Dial-Up/Leased Line)  
DOWN  
#2  
SDLC*/BSC (Sync)  
UP*  
DOWN  
#3  
Result Codes Enable*/Disable  
(Async/Dial-up)  
UP  
DOWN*  
#3  
DbM Transmit (-9db/0dB)*/(-15db/-10dB) UP  
(Async/Sync/Lease-Line)  
DOWN*  
#4  
UUCP Enable/Disable*  
UP*  
(Async/Dial-Up/Leased Line)  
DOWN  
#4  
AS/400 Enable/Disable*  
UP*  
(Sync/Dial-Up/Leased line)  
DOWN  
#5  
Auto-Answer Enable*/Disable  
(Async/Sync/Dial-Up)  
UP*  
DOWN  
#5  
Answer*/Originate  
(Async/Sync/Leased Line)  
DOWN  
UP*  
#6  
Max-Thru Enable*/Disable  
(Async/Dial-Up/Leased)  
UP*  
DOWN  
#6  
Slave Clock Enable/Disable*  
(Sync/Dial-Up/Leased)  
UP*  
DOWN  
#7  
RTS/Normal/Forced*  
UP  
(Sync/Async/Dial/Leased)  
DOWN*  
#8  
Command Mode Enabled*  
(Sync/Async/Dial/Leased)  
UP  
DOWN*  
#9  
Local/Remote* LoopBack  
(Async/Sync/Dial/Leased)  
UP  
DOWN*  
#10  
#11  
#11  
#12  
Dial-Up*/Leased-Line  
UP*  
DOWN  
"AT"/"Multi-Tech" Result Codes*  
(Asynchronous)  
UP  
DOWN*  
Internal*/External Clocking  
(Synchronous)  
UP  
DOWN*  
Sync/Async Mode*  
UP  
DOWN*  
* Factory Default Setting  
115  
 
MultiModemBL User Guide  
DIP Switches #13-14  
Note: The modem baud rate command ($MBn) overrides the setting of these speed selection  
switches (DIP switches #13 and #14).  
2834 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
1932 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
1432 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
CONDITION  
UP/UP*  
EFFECT  
28.8 K bps Operation  
19.2 K bps Operation  
14.4 K bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 9600 bps Operation  
CONDITION  
UP/UP*  
EFFECT  
19.2 K bps Operation  
14.4 K bps Operation  
9600 bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 2400 bps Operation  
CONDITION  
UP/UP*  
EFFECT  
14.4 K bps Operation  
9600 bps Operation  
4800 bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 2400 bps Operation  
DIP Switches #15-16  
#15  
#15  
#16  
#16  
UP*  
CD/DSR from Interface  
CD/DSR Forced On  
2-Wire Leased Line  
4-Wire Leased Line  
DOWN  
UP  
DOWN*  
*Standard Factory Default Setting  
116  
 
Chapter 10 - Warranty, Service and Tech Support  
 
MultiModemBL User Guide  
10.1 Introduction  
This chapter starts out with statements about your modem's 5-year warranty. The next section, Tech  
Support, should be read carefully if you have questions or problems with your modem. It includes the  
technical support telephone numbers, space for recording your modem information, and an  
explanation of how to send in your modem should you require service. The final four sections explain  
how to use our Bulletin Board Service (BBS), upgrading the modem via Flash PROM, a brief section  
on the CompuServe/Internet forums and information on Multi-Tech's Fax-Back Service.  
10.2 Limited Warranty  
Multi-Tech Systems, Inc. (“MTS”) warrants that its products will be free from defects in material or  
workmanship for a period of five years from the date of purchase, or if proof of purchase is not  
provided, five years from date of shipment. MTS MAKES NO OTHER WARRANTY, EXPRESSED  
OR IMPLIED, AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A  
PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. This warranty does not apply to any  
products which have been damaged by lightning storms, water, or power surges or which have been  
neglected, altered, abused, used for a purpose other than the one for which they were manufactured,  
repaired by the customer or any party without MTS’s written authorization, or used in any manner  
inconsistent with MTS’s instructions.  
MTS’s entire obligation under this warranty shall be limited (at MTS’s option) to repair or replacement  
of any products which prove to be defective within the warranty period, or, at MTS’s option, issuance  
of a refund of the purchase price. Defective products must be returned by Customer to MTS’s factory  
transportation prepaid.  
MTS WILL NOT BE LIABLE FOR CONSEQUENTIAL DAMAGES AND UNDER NO  
CIRCUMSTANCES WILL ITS LIABILITY EXCEED THE PURCHASE PRICE FOR DEFECTIVE  
PRODUCTS.  
10.2.1 On-line Warranty Registration  
To register your MultiModem on-line, click on the following link:  
118  
 
Chapter 10 - Warranty, Service and Tech Support  
10.3 Tech Support  
Multi-Tech has an excellent staff of technical support personnel available to help you get the most out  
of your Multi-Tech product. If you have any questions about the operation of this unit, call 1-800-972-  
2439. Please fill out the modem information (below), and have it available when you call. If your  
modem requires service, the tech support specialist will guide you on how to send in your modem  
(see Section 10.3.2).  
10.3.1 Recording Modem Information  
Please fill in the following information on your Multi-Tech modem. This will help tech support in  
answering your questions.  
Modem Model No.:  
Modem Serial No.:  
Modem Firmware Version:  
COM Port #:  
FAX Software Type and Version:  
DataComm Software Type and Version:  
The modem model and serial numbers are silkscreened on the bottom of your modem. The software  
versions are printed on the diskette labels. Type ATI1 to display the modem firmware version.  
Please note the status of your modem before calling tech support. This status can include LED  
indicators, screen messages, diagnostic test results, problems with a specific application, etc. Use  
the space below to note modem status:  
10.4 Service  
If your tech support specialist decides that service is required, modems may be sent (freight prepaid)  
to our factory. Return shipping charges will be paid by Multi-Tech Systems (within North America).  
Include the following with your modem:  
a description of the problem.  
return billing and return shipping addresses.  
contact name and phone number.  
check or purchase order number for payment if the modem is out of warranty. (The standard  
repair charge for this modem is $95. This price is valid at the time of this publication but could  
change in the future. Check with your technical support specialist.)  
if possible, note the name of the technical support specialist with whom you spoke.  
If you need to inquire about the status of the returned product, be prepared to provide the serial  
number of the product sent (see Section 10.3.1).  
Send modems to this address:  
MULTI-TECH SYSTEMS, INC.  
2205 WOODALE DRIVE  
MOUNDS VIEW, MINNESOTA 55112  
ATTN: SERVICE OR REPAIRS  
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MultiModemBL User Guide  
10.5 The Multi-Tech BBS  
For customers who do not have Internet access, Multi-Tech maintains a bulletin board system (BBS)  
that mirrors its FTP site. Information available from the BBS includes new product information,  
product upgrade files, and problem-solving tips. The phone number for the Multi-Tech BBS is (800)  
392-2432 (USA and Canada) or (612) 785-3702 (international and local).  
The BBS can be accessed by any asynchronous modem operating at 1200 bps to 33,600 bps at a  
setting of 8 bits, no parity, and 1 stop bit (8-N-1).  
To log on to the Multi-Tech BBS  
1. Set your communications program to 8-N-1.  
2. Dial our BBS at (800) 392-2432 (USA and Canada) or (612) 785-3702 (international and local).  
3. At the prompts, type your first name, last name, and password; then press ENTER. If you are a  
first time caller, the BBS asks if your name is spelled correctly. If you answer yes, a  
questionnaire appears. You must complete the questionnaire to use the BBS on your first call.  
4. Press ENTER until the Main Menu appears. From the Main Menu you have access to two areas:  
the Files Menu and News. For help on menu commands, type ?.  
To Download a file  
If you know the file name  
1. From the Main Menu, type F to access the Files Menu, then type D.  
2. Enter the name of the file you wish to download from the BBS.  
3. If a password is required, enter the password.  
4. Answer Y or N to the automatic logoff question.  
5. Select a file transfer protocol by typing the indicated letter, such as Z for Zmodem (the  
recommended protocol).  
6. If you select Zmodem, the transfer will begin automatically. If you select another protocol, you  
may have to initiate the transfer yourself. (In most datacomm programs, the PAGE DOWN key  
initiates the download.)  
7. When the download is complete, press ENTER to return to the File Menu.  
8. To exit the BBS, type G and press ENTER.  
If you don’t know the file name  
1. From the Main Menu, type F to access the Files Menu. For a list of file areas, type L, press  
ENTER, then type L and press ENTER again. (If you do not type the second L, you will list all of  
the files on the BBS.)  
2. Mark each file area you would like to examine by typing its list number and pressing ENTER.  
3. Enter L to list all the files in the selected file areas. Enter C to go forward in the file list and P to  
go back.  
4. To mark one or more files for download, type M, press ENTER, type the list numbers of the files,  
and press ENTER again.  
5. Enter D. You will see a list of the files you have marked. Enter E if you would like to edit the list;  
otherwise enter D again to start the download process.  
6. Select a file transfer protocol by typing the indicated letter, such as Z for Zmodem (the  
recommended protocol).  
7. If you select Zmodem, the file will transfer automatically. If you select another protocol, you may  
have to initiate the transfer yourself. (In most data communications programs, the PAGE DOWN  
key initiates the download.)  
8. When the download is complete, press ENTER to return to the File Menu.  
9. To exit the BBS, type G and press ENTER.  
120  
 
Chapter 10 - Warranty, Service and Tech Support  
10.5.1 Upgrading the MultiModem  
The MultiModem has a Flash PROM which contains firmware code for the hardware and DSP code  
for the digital signal processor chips. At various times, Multi-Tech may add enhancements and/or  
fixes to the firmware. The flash technology used in the MultiModem lets you load these upgrades into  
the PROM or DSP chips through the modem's serial port.  
10.5.2 Using FlashPro to Upgrade Modem Firmware  
1. Download FLASHPRO.ZIP and a new .HEX file from the Multi-Tech BBS.  
2. Unzip the FLASHPRO.ZIP file. Place this unzipped file and the .HEX file in the same directory.  
3. Run FlashPro by typing FLASHPRO, a space, -M and hitting ENTER at the DOS prompt.  
4. Highlight the "Configure" option in the MAIN MENU and hit ENTER. Highlight "Active Port" and  
select the COM port to which you have your modem attached. Highlight "Baud Rate" and select  
the rate you want to program at. Hit ESC when finished.  
5. Highlight the "Select File to Program" option in the MAIN MENU. Highlight the .HEX file. Hit ESC  
when finished.  
6. Highlight "Program Firmware" option in the MAIN MENU. When you are prompted to confirm the  
file to program, press "Y".  
7. If you need more assistance programming FLASHPRO, then contact our tech support  
department.  
10.6 About Multi-Tech’s Internet Presence  
Multi-Tech's presence includes a Web site at:  
and an ftp site at:  
10.7 About the Multi-Tech Fax-Back Service  
Multi-Tech's fax-back system provides 24-hour access to sales, marketing, and technical literature.  
Dial 612-717-5888, follow the voice prompts, and request document number 10 for a catalog of  
available documents.  
For convenience, have your fax number handy: __________________ . From the catalog of  
available documents, you can order newsletters, white papers, press releases, etc. from the sales  
and marketing index (pages 1-4), or order basic modem operation and troubleshooting guides from  
the technical support and engineering index. Just enter the applicable FB Doc. # from the left column  
of the catalog.  
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MultiModemBL User Guide  
10.8 About Ordering Accessories  
SupplyNet, Inc. can supply you with replacement transformers, cables and connectors for select  
Multi-Tech products. You can place an order with SupplyNet via mail, phone, fax or the Internet at:  
Mail:  
SupplyNet, Inc.  
614 Corporate Way  
Valley Cottage, NY 10989  
Phone:  
Fax:  
800 826-0279  
914 267-2420  
Email:  
info@thesupplynet.com  
SupplyNet Online Ordering Instructions  
1. Browse to http://www.thesupplynet.com. In the Browse by Manufacturer drop-down list,  
select Multi-Tech and click  
2. To order, type in quantity, and click  
3. Click  
to change your order  
4. After you have selected all of your items click  
to finalize the order. The SupplyNet  
site uses Verisign’s Secure Socket Layer (SSL) technology to ensure your complete shopping  
security.  
122  
 
Appendixes  
 
MultiModemBL User Guide  
Appendix A - Troubleshooting  
Your modem was thoroughly tested at the factory before it was shipped. If you are unable to make a  
successful connection or if you experience data loss or garbled characters during your connection, it  
is possible that the modem is defective. However, it is more likely that the source of your problem lies  
elsewhere. Problems you may encounter include the following:  
None of the LEDs light when the modem is on.  
The modem does not respond to commands.  
The modem dials but is unable to make a connection.  
The modem disconnects while on-line.  
The modem cannot connect when answering.  
File transfer is slower than it should be.  
I am losing data.  
I am getting garbage characters on the monitor.  
I can’t run my fax and communications software at the same time.  
If you experience problems, please check the following possibilities before calling Tech Support (see  
Chapter 10).  
None of the LEDs Light When the Modem Is On  
When you turn on the modem, the LED indicators on the front panel should flash briefly as the  
modem runs a self-test. If the LEDs remain off, the modem is probably not receiving power.  
Make sure the modem’s power switch is on, especially if you normally turn on the modem by  
turning on a power strip.  
If the power supply is plugged into a power strip, make sure the power strip is plugged in and its  
power switch is on.  
Make sure the power supply module is firmly connected to the modem and to the wall outlet or  
power strip.  
If the power strip is on and the modem switch is on, try moving the modem power supply to  
another outlet on the power strip.  
Test that the outlet is live by plugging a lamp into it.  
The modem or power supply may be defective. If you have another Multi-Tech modem, try  
swapping modems. If the problem goes away, the first modem or power supply may be defective.  
Call Tech Support for assistance.  
CAUTION: Do not under any circumstances replace the power supply module with one designed for  
another product, as it may damage the modem and void your warranty.  
The Modem Does Not Respond to Commands  
Make sure the modem is plugged in and turned on. (See “None of the LEDs Light When the  
Modem Is On.”)  
Make sure you are issuing the modem commands from the data communications software, either  
manually in terminal mode or automatically by configuring the software. (You cannot send  
commands to the modem from the DOS prompt.)  
Make sure you are in terminal mode in your data communications program, then type AT and  
press ENTER. If you get an OK response, your connections are good and the problem likely is in  
your phone book entry or session settings.  
Try resetting your modem by turning it off and on. Make sure there is a reset command (&F) in  
your initialization string, or your modem may not initialize correctly.  
124  
 
Appendix A - Troubleshooting  
If you don’t get an OK, the problem may still be in the communications software. Make sure you  
have done whatever is necessary in your software to make a port connection. Not all  
communications programs connect to the COM port automatically. Some connect when the  
software loads and remain connected until the program terminates. Others can disconnect  
without exiting the program (make sure the Connect icon looks plugged in). If the terminal reports  
that it cannot make a connection, yet the modem’s TR indicator is on, click on the Window menu  
to see if more than one terminal is open. The modem’s TR indicator shows that the software has  
made a connection with the modem through the COM port.  
Your communications software settings may not match the physical port the modem is connected  
to. The serial cable may be plugged into the wrong connector—check your computer  
documentation to make sure. Or you may have selected a COM port in your software other than  
the one the modem is physically connected to—compare the settings in your software to the  
physical connection.  
If the modem is on, the cable is plugged into the correct port, the communications software is  
configured correctly, and you still don’t get an OK, the fault may be in the serial cable. Make sure  
it is firmly connected at both ends.  
Is this the first time you have used the cable? If so, it may not be correct. Check the cable  
description on the packaging to make sure the cable is the right one for your computer.  
Peripheral expansion cards, such as bus mouse and sound cards, may include a serial port pre-  
configured as COM1 or COM2. The extra serial port, or the card itself, may use the same COM  
port, memory address, or interrupt request (IRQ) as your communications port. Be sure to  
disable any unused ports.  
To look for address or IRQ conflicts if you use Windows 3.1x, select File, Run in Program  
Manager, type MSD, and press ENTER. Then select Mouse, COM Ports, and IRQ Status and  
note the addresses and IRQs that are in use. If you find an IRQ conflict, note which IRQs are not  
being used, then change one of the conflicting devices to use one of the unused IRQs. If you find  
an address conflict, change the address of one of the conflicting devices.  
To change a port address or IRQ in Windows 3.1x, double-click the Control Panel icon, then the  
Ports icon. Click on the port you want to change, click Settings, click Advanced, and select the  
new port address and/or interrupt. If you wish to use COM3 or COM4, note that COM3 shares an  
IRQ with COM1, as does COM4 with COM2, so you should change their IRQs to unused ones, if  
possible.  
If you use Windows 95, right-click on My Computer, select Properties from the menu, click on the  
Device Manager tab, double-click on Ports, then double-click on the Communications Port your  
modem is connected to. In the port’s Properties sheet, click on the Resources tab to see the  
port’s Input/Output range and Interrupt Request. If another device is using the same address  
range or IRQ, it will appear in the Conflicting Device List. Uncheck Use Automatic Settings to  
change the port’s settings so they do not conflict with the other device, or select the port the  
conflicting device is on and change it instead. If you need to open your computer to change  
switches or jumpers on the conflicting device; refer to the device’s documentation.  
The serial port may be defective. If you have another serial port, install the modem on it, change  
the COM port setting in your software, and try again.  
The modem may be defective. If you have another Multi-Tech modem, try swapping modems. If  
the problem goes away, the first modem is possibly defective. Call Tech Support for assistance  
(see Chapter 10).  
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MultiModemBL User Guide  
The Modem Dials But Cannot Make a Connection  
There can be several reasons the modem fails to make a connection. Possibilities include  
lack of a physical connection to the telephone line.  
a wrong dial tone.  
a busy signal.  
a wrong number.  
no modem at the other end.  
a faulty modem, computer, or software at the other end.  
incompatibility between modems.  
You can narrow the list of possibilities by using extended result codes. To enable them, enter  
ATV1X4 and press ENTER while in terminal mode, or include V1X4 in the modem’s initialization  
string. When you dial again, the modem will report the call’s progress.  
If the modem reports NO DIALTONE, check that the modem’s telephone line cable is connected  
to both the modem’s LINE jack (not the PHONE jack) and the telephone wall jack. If the cable  
looks secure, try replacing it. If that doesn’t work, the problem may be in your building’s  
telephone installation. To test the building installation, plug a telephone into your modem’s  
telephone wall jack and listen for a dial tone. If you hear a dial tone, your modem may be  
installed behind a company phone system (PBX) with an internal dial tone that sounds different  
from the normal dial tone. In that case, the modem may not recognize the dial tone and may treat  
it as an error. Check your PBX manual to see if you can change the internal dial tone; if you  
can’t, change your modem’s initialization string to replace X4 with X3, which will cause the  
modem to ignore dial tones.  
If the modem reports BUSY, the other number may be busy, in which case you should try again  
later, or it may indicate that you have failed to add a 9, prefix to the phone number if you must  
dial 9 for an outside line.  
If you must dial 9 to get an outside line, the easiest way to dial it automatically is to include it in  
the modem’s dial prefix, e.g., ATDT9,. Note the comma, which inserts a pause before the  
number is dialed. By inserting 9, into the dial prefix, you do not have to include it in each directory  
entry in the terminal.  
To change the dial prefix in Windows Terminal, select Settings, Modem Commands. To change it  
in Windows 95 HyperTerminal, select Call, Connect from the menu bar, click Dialing Properties,  
and type 9 in the local and long distance boxes in How I Dial from This Location.  
If the modem reports NO ANSWER, the other system has failed to go off-hook, or you might  
have dialed a wrong number. Check the number.  
If the modem reports NO CARRIER, the phone was answered at the other end, but no  
connection was made. You might have dialed a wrong number, and a person answered instead  
of a computer, or you might have dialed the correct number but the other computer or software  
was turned off or faulty. Check the number and try again, or try calling another system to make  
sure your modem is working. Also, try calling the number on your telephone. If you hear harsh  
sounds, then another modem is answering the call, and the modems may be having problems  
negotiating because of modem incompatibilities or line noise. Try connecting at a lower speed.  
126  
 
Appendix A - Troubleshooting  
The Modem Disconnects While On-line  
If you have call waiting on the same phone line as your modem, it may interrupt your connection  
when someone tries to call you. If you have call waiting, disable it before each call. In most  
telephone areas, you can disable call waiting by preceding the telephone number with *70 (check  
with your local telephone company).  
You can automatically disable call waiting by including the disabling code in the modem’s dial  
prefix (e.g., ATDT*70,—note the comma, which inserts a pause before the number is dialed). To  
change the dial prefix in Windows Terminal, select Settings, Modem Commands. To change it in  
Windows 95 HyperTerminal, select Call, Connect from the menu bar, click Dialing Properties,  
check this location has Call Waiting, and select the correct code for your phone service.  
If you have extension phones on the same line as your modem, you or someone else can  
interrupt the connection by picking up another phone. If this is a frequent problem, disconnect the  
extension phones before using the modem, or install another phone line especially for the  
modem.  
Check for loose connections between the modem and the computer, the telephone jack, and AC  
power.  
You may have had a poor connection because of line conditions or the problem may have  
originated on the other end of the line. Try again.  
If you were on-line with a BBS, it may have hung up on you because of lack of activity on your  
part or because you exceeded your time limit for the day. Try again.  
The Modem Cannot Connect When Answering  
Auto-answer may be disabled. Turn on auto-answer in your datacomm program or send the  
command ATS0=1 to your modem in terminal mode.  
File Transfer Is Slower Than It Should Be  
You may have an older UART. For best throughput, install a 16550AFN UART or a Multi-Tech ISI  
serial port card. See the “Quick Start” chapter for information on how to identify your UART.  
If you are running under Windows 3.1 and have a 16550AFN UART, you must replace the  
Windows serial driver, COMM.DRV, to take full advantage of the UART’s speed.  
If you are using a slow transfer protocol, such as Xmodem or Kermit, try Zmodem or Ymodem/G  
instead.  
Is your line noisy? If there is static on your line, the modem has to re-send many blocks of data to  
insure accuracy. You must have a clean line for maximum speed.  
Are you downloading a compressed file with MNP 5 hardware compression enabled? Since  
hardware data compression cannot compress a file already compressed by an archiving  
program, the transfer can be marginally slower with data compression enabled than with it  
disabled.  
Try entering the L8 (List Online Diagnostics) command in on-line mode, making a screen print of  
the diagnostics listing, and checking for parameters that may be unacceptable (number of  
retrains, round trip delay, etc.).  
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MultiModemBL User Guide  
I Am Losing Data  
If you are using data compression and a high speed serial port, set the serial port baud rate to  
four times the data rate.  
Your UART may not be reliable at serial port speeds over 9600 bps or 19,200 bps. Turn off data  
compression, reset your serial port speed to a lower rate, or replace your serial port with a faster  
one.  
Make sure the flow control method you selected in software matches the method selected in the  
modem. If you have a Macintosh, you may have the wrong cable for hardware flow control.  
If you are running under Windows 3.1 and have a 16550AFN UART, you may need to turn on the  
16550’s data buffers and/or replace the Windows serial driver, COMM.DRV.  
Try entering the L8 (List Online Diagnostics) command in on-line mode, making a screen print of  
the diagnostics listing, and checking for parameters that may be unacceptable (number of  
retrains, round trip delay, etc.).  
I Am Getting Garbage Characters on the Monitor  
Your computer and the remote computer may be set to different word lengths, stop bits, or  
parities. If you have connected at 8-N-1, try changing to 7-E-1, or vice-versa, using your  
communications software.  
You may be experiencing line noise. Enable error correction, if it is disabled, or hang up and call  
again; you may get a better connection.  
At speeds above 2400 bps, the remote modem might not use the same transmission or error  
correction standards as your modem. Try connecting at a slower speed or disabling error  
correction. (With no error correction, however, line noise can cause garbage characters.)  
Try entering the L8 (List Online Diagnostics) command in on-line mode, making a screen print of  
the diagnostics listing, and checking for parameters that may be unacceptable (number of  
retrains, round trip delay, etc.).  
My Fax and Communications Software Won’t Run at the Same Time  
Communications devices can be accessed by only one application at a time. Under DOS or Windows  
3.1x, you can run either your fax software or your datacomm software, but not both at the same time,  
unless you have a special communications device management application, such as Multi-Tech’s  
Virtual Modem Driver. In Windows 95, you can have data and fax communication applications open  
at the same time, but they cannot use the same modem at the same time.  
128  
 
Appendix B - ASCII Conversion Chart  
Appendix B - ASCII Character Code/Hex/Decimal Conversion Chart  
CTRL CODE HEX DEC CODE HEX DEC CODE HEX DEC CODE HEX DEC  
@ NUL  
00  
0
1
2
3
4
5
6
7
8
9
SP  
!
#
$
%
&
(
)
*
=
,
20  
21  
22  
23  
24  
25  
26  
27  
28  
29  
2A 42  
2B 43  
2C 44  
2D 45  
2E 46  
2F  
30  
31  
32  
33  
34  
35  
36  
37  
38  
39  
3A 58  
3B 59  
3C 60  
3D 61  
3E 62  
32  
33  
34  
35  
36  
37  
38  
39  
40  
41  
@
A
B
C
D
E
F
G
H
I
40  
41  
42  
43  
44  
45  
46  
47  
48  
49  
4A 74  
4B 75  
4C 76  
4D 77  
4E 78  
4F  
50  
51  
52  
53  
54  
55  
56  
57  
58  
59  
5A 90  
5B 91  
5C 92  
5D 93  
5E 94  
64  
65  
66  
67  
68  
69  
70  
71  
72  
73  
60 96  
61 97  
62 98  
63 99  
64 100  
65 101  
66 102  
67 103  
68 104  
69 105  
6A 106  
6B 107  
6C 108  
6D 109  
6E 110  
6F 111  
70 112  
71 113  
72 114  
73 115  
74 116  
75 117  
76 118  
77 119  
78 120  
79 121  
7A 122  
7B 123  
7C 124  
7D 125  
7E 126  
7F 127  
A
B
C
D
E
F
G
H
I
SOH 01  
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
{
|
STX  
ETX  
EOT  
02  
03  
04  
ENQ 05  
ACK  
BEL  
BS  
06  
07  
08  
09  
0A 10  
0B 11  
0C 12  
0D 13  
0E 14  
0F  
10  
11  
12  
13  
14  
15  
16  
17  
HT  
J
LF  
J
K
L
K
L
VT  
FF  
M
N
O
P
Q
R
S
T
U
V
CR  
SO  
SI  
DLE  
DC1  
DC2  
DC3  
DC4  
NAK  
SYN  
-
.
/
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
[
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
47  
48  
49  
50  
51  
52  
53  
54  
55  
56  
57  
79  
80  
81  
82  
83  
84  
85  
86  
87  
88  
89  
0
1
2
3
4
5
6
7
8
9
:
W ETB  
X
Y
Z
[
CAN 18  
EM  
SUB  
ESC  
FS  
19  
1A 26  
1B 27  
1C 28  
1D 29  
1E 30  
;
\
<
=
>
?
\
]
^
_
]
GS  
}
RS  
— US  
DEL  
1F  
31  
3F  
63  
5F  
95  
NUL  
Null, or all zeros  
DC1  
Device Control 1  
Device Control 2  
Device Control 3  
Device Control 4  
SI  
Shift In  
Shift Out  
Sync.  
Line Feed  
Form Feed  
SOH Start of Header  
DC2  
DC3  
DC4  
SO  
SYN  
LF  
STX  
ETX  
EOT  
ACK  
BEL  
BS  
HT  
VT  
ETB  
Start of Text  
End of Text  
End of Transmission  
Acknowledge  
Bell or Alarm  
Backspace  
Horizontal Tab  
Vertical Tab  
End Transmission Block  
CAN Cancel  
FF  
EM  
SUB  
FS  
GS  
RS  
End of Medium  
Substitute  
File Separator  
Group Separator  
Record Separator  
Delete  
ENQ Enquiry  
ESC  
DLE  
NAK  
CR  
Escape  
Data Link Escape  
Negative Acknowledge  
Carriage Return  
DEL  
129  
 
MultiModemBL User Guide  
Appendix C - Dial Pulse and Tone-Dial Frequencies  
Dial Pulses  
B
Closed  
A
Open  
Digit 2  
Digit 1  
In the example above, the digit 2 is pulse dialed, followed by the digit 1. Each pulse consists of an A  
mSec. open and a B mSec. closed, where A will be either 60 or 67 mSec and B will be either 40 or 33  
mSec., for a total of 100 mSec. per pulse, or a rate of 10 pulses per second. The interdigital pause  
time is 800 mSec. The pulse ratios are controlled by the &P command.  
Tone Dial Frequencies  
Hz  
Digits  
697  
770  
852  
941  
1
4
7
2
5
8
3
6
9
A
B
C
0
#
D
*
Hz 1209  
1336  
1477  
1633  
130  
 
Appendix D - AT Command Summary  
Appendix D - Command Summary  
Command  
Values  
Description  
AT  
Attention Code that precedes most command strings  
except A/, A: and Escape Codes.  
RETURN  
$
Pressing RETURN key executes most commands.  
This symbol placed in dialing string enables the  
modem to detect AT&T's "call card" tones for  
accessing user's calling card to originate an on-line  
connection.  
A
Answer call, even if no ring present. Repeat last  
command. (Do not precede this command with AT.  
Do not hit RETURN to execute.)  
***A:  
$An  
#An  
Continuous redial (10 redials in DOC units) of last  
number until answered. (Not used Internationally.)  
n = 0 or 1  
*
*
$A0 discards data during auto-reliable time period.  
$A1 buffers data during auto-reliable time period.  
n = 0 thru 3  
2834 Series:  
#A0 selects initial handshake at:33,600 to 31,200 to  
28,800 to 24000 to 21,600 to 19,200 to 16,800 to  
14,400 to 12,000 to 9600 to 4800 to 2400 to 1200 to  
300 bps.  
#A1 selects initial handshake at 33,600 bps only.  
#A2 selects initial handshake at 33,600 to 31,200 to  
28,800 to 24000 to 21600 to 19,200 to 16,800  
19,200 to 14,400 to 9600 to 4800 bps.  
#A3 selects initial handshake at 2400 to 1200 to 300  
bps.  
1932 Series:  
*
#A0 selects initial handshake at: 19,200 to 16,800 to  
14,400 to 12,000 to 9600 to 4800 to 2400 to 1200 to  
300 bps.  
#A1 selects initial handshake at 19,200 bps only.  
#A2 selects initial handshake at 19,200 to 16,800 to  
14,400 to 9600 to 4800 bps.  
#A3 selects initial handshake at 2400 to 1200 to 300  
bps.  
1432 Series:  
*
#A0 selects initial handshake at: 14,400 to 12,000 to  
9600 to 4800 to 2400 to 1200 to 300 bps.  
#A1 selects initial handshake at 14,400 bps only.  
#A2 selects initial handshake at 14,400 to 9600 to  
4800 bps.  
#A3 selects initial handshake at 2400 to 1200 to 300  
bps.  
* Factory Default Setting  
*** Not applicable in BLK models  
131  
 
MultiModemBL User Guide  
Command  
Values  
Description  
***Bn  
n = 0 or 1  
*
*
B0 selects V.21 answer tone.  
B1 selects Bell answer tone.  
&Bn  
n = 0 or 1  
n = 0 or 1  
&B0 means normal transmit buffer size.  
&B1 means reduced transmit buffer size.  
&BSn  
&BS0 means maximum transmit block size of 64  
characters.  
*
*
&BS1 means maximum transmit block size of 256  
characters.  
$BAn  
n = 0 or 1  
$BA0 means speed conversion is on.  
$BA1 means speed conversion is off.  
&Cn  
n = 0,1,2,4  
&C0 forces Carrier Detect on.  
*
*
&C1 lets Carrier Detect act normally.  
&C2 lets Carrier Detect drop S24 time on  
disconnect.  
&C4 resets modem when Carrier Detect drops.  
&CDn  
Ds  
n = 0 or 1  
&CD0 execute cleardown on disconnect.  
&CD1 do not execute cleardown on disconnect.  
s = phone #  
s = phone #  
Dial a telephone number “s,” where s may include  
up to 60 digits or T, P, R, comma and ; characters.  
DsNd  
Store telephone number. To store, phone d = 0 thru  
9 number ”s“ is entered and followed by N and then  
Directory Number “d.”  
&Dn  
n = 0 thru 3  
** &D0 DTR is ignored  
&D1 means modem returns to command mode.  
*
&D2 lets modem react to DTR normally.  
&D3 causes modem to reset to modem default  
parameters.  
%DFn  
n = 0 or 1  
n = 0 or 1  
*
*
%DF0 Line Probe Data in Graph Format.  
%DF1 Line Probe Data in Table Format.  
%DPn  
%DP0 do not read Line Probe Information from DSP  
during handshaking.  
%DP1 read Line Probe Information from DSP during  
handshaking.  
$Dn  
n = 0 or 1  
n = 0 or 1  
*
*
$D0 disables DTR Dialing.  
$D1 enables DTR Dialing.  
En  
E0 means do not echo Command Mode Character.  
E1 means do echo Command Mode characters.  
* Factory Default Setting  
** Factory Default Setting for BL-Mac  
*** Not applicable in BLK models  
132  
 
Appendix D - AT Command Summary  
Command  
Values  
Description  
&En  
n = 0 thru 15  
&E0 means no error correction.  
*
&E1 means V.42 Auto-reliable Mode.  
&E2 means V.42 Reliable Mode.  
&E3 means no modem-initiated flow control.  
&E4 means CTS modem-initiated flow control.  
&E5 means Xon/Xoff modem-initiated flow control.  
&E6 means Xon/Xoff not passed through.  
&E7 means Xon/Xoff passed through.  
&E8 means Enq/Ack pacing off.  
*
*
*
*
&E9 means Enq/Ack pacing on.  
&E10 means Normal Mode flow control off.  
&E11 means Normal Mode flow control on.  
&E12 means Pacing off.  
*
&E13 means Pacing on.  
&E14 means data compression disabled.  
&E15 means data compression enabled.  
*
*
$EBn  
n = 0 or 1  
n=0 thru 5  
$EB0 enables 10 bit mode.  
$EB1 enables 11 bit mode.  
%En  
% E0 = Modem Won’t Escape.  
% E1 = +++ Method (default setting).  
% E2 = Break Method.  
*
% E3 = Either +++ or Break Method.  
% E4 = No "OK" Response to +++  
% E5 = "OK" Response to +++  
#Fn  
n = 0 thru 2  
n = 0, 8 or 9  
#F0 means no fallback when on-line.  
#F1 means fallbackwhen on-line (increments of  
2400 bps).  
#F2 means fallback to 4800 bps/fall forward if line  
improves (increments of 2400 bps).  
*
*
&Fn  
&F loads factory default values from ROM.  
&F8 reads factory default values and switch settings  
when &F is issued.  
&F9 reads parameters stored in non-volatile  
memory when &F is issued.  
$FCn  
n = 0 or 1  
n = 0 or 1  
$FC0 means no transmit of 5 second 2100Hz signal.  
$FC1 transmits 5 second 2100Hz signal.  
*
$Fn  
$F0 means do not fall back to normal connect if CR  
received.  
*
*
$F1 means fall back to normal connect if CR  
received.  
***&Gn  
n = 0, 1 or 2  
n = 0 or 1  
&G0 turns off CCITT guard tones.  
&G1 turns on CCITT 550 Hz guard tone.  
&G2 turns on CCITT 1800 Hz guard tone.  
Hn  
H0 means Hang Up (go on hook).  
H1 means Go Off Hook.  
* Factory Default Setting  
*** Not applicable in BLK models  
133  
 
MultiModemBL User Guide  
Command  
Values  
Description  
$Hn  
n = 1 thru 3  
$H1 brings up Help Screen #1.  
$H2 brings up Help Screen #2.  
$H3 brings up Help Screen #3.  
In  
n = 0,1or 2  
Read Only  
I0 requests modem ID #.  
I1 requests firmware revision #.  
I2 for MTS internal use.  
I9 (2834 Series only)  
Command enables display of Windows 95  
Autodetect characteristics  
L
Lists all stored telephone numbers in memory.  
L5 lists all current operating parameters.  
L6 lists all current S-Register values.  
L7 lists additional parameters.  
L5  
L6  
L7  
L8  
L8 lists On-Line Diagnostics.  
L9  
L9 Displays Signal Strength Information.  
L10 Displays Signal to Noise Ratio Information.  
L11 Displays Noise Information.  
L10  
L11  
#Ln  
n = 0 thru 3  
n = 0 thru 3  
n = speed  
*
*
#L0 means modems negotiate V.42 Mode.  
#L1 means MNP on and LAP-M off.  
#L2 means LAP-M on and MNP off.  
#L3 means no detection phase but go directly to  
LAP-M.  
Mn  
M0 means Monitor speaker always Off.  
M1 means Monitor speaker On until carrier detected  
M2 means Monitor speaker always On.  
M3 Monitor speaker on during dialing/off during  
handshaking.  
$MBn  
2834 Series:  
$MB75 selects CCITT V.23 mode.  
$MB300 selects 300 bps on-line.  
$MB1200 selects 1200 bps on-line.  
$MB2400 selects 2400 bps on-line.  
$MB4800 selects 4800 bps on-line.  
$MB9600 selects 9600 bps on-line.  
$MB14400 selects 14400 bps on-line  
$MB19200 selects 19200 bps on-line  
$MB28800 selects 28800 bps on-line  
$MB33600 selects 33600 bps on-line  
*
1932 Series:  
$MB75 selects CCITT V.23 mode.  
$MB300 selects 300 bps on-line.  
$MB1200 selects 1200 bps on-line.  
$MB2400 selects 2400 bps on-line.  
$MB4800 selects 4800 bps on-line.  
$MB9600 selects 9600 bps on-line.  
$MB14400 selects 14400 bps on-line  
$MB19200 selects 19200 bps on-line  
*
* Factory Default Setting  
134  
 
Appendix D - AT Command Summary  
Command  
Values  
Description  
1432 Series:  
$MB75 selects CCITT V.23 mode.  
$MB300 selects 300 bps on-line.  
$MB1200 selects 1200 bps on-line.  
$MB2400 selects 2400 bps on-line.  
$MB4800 selects 4800 bps on-line.  
$MB9600 selects 9600 bps on-line.  
$MB14400 selects 14400 bps on-line  
*
*
&Mn  
Nd  
n = 0 or 1  
&M0 selects Async when on-line.  
&M1 selects Sync when on-line.  
d = 0 thru 9  
Dial stored telephone number “d” (Do not include the  
letter D in this command.)  
NdNe  
d = 0 thru 9  
e = any other  
number 0  
thru 9  
Number Linking. If first number dialed is  
busy, another stored number may be  
automatically dialed. In example, stored  
number d is dialed, and if busy, stored  
number e is dialed.  
O
Exit Command Mode and go into On-Line Mode.  
Modem will pulse-dial numbers following the P.  
P
*
*
***&Pn  
n = 0 or 1  
&P0 means 60-40 pulse ratio.  
&P1 means 67-33 pulse ratio.  
Qn  
n = 0, 1 or 2  
*
Q0 means Result Codes sent.  
Q1 means Result Codes will be suppressed (quiet).  
Q2 means Dumb Answer Mode.  
&Qn  
Rn  
n = 0 or 1  
n = 0 or 1  
n = 0, 1 or 2  
*
*
&Q0 selects Multi-Tech command set.  
&Q1 selects AT command set.  
R0 means modem will not reverse modes.  
R1 means modem will reverse modes.  
&Rn  
&R0 lets Clear to Send act normally.  
&R1 forces Clear to Send on.  
*
&R2 drops for 1 second on disconnect.  
&RP  
Command Initiates a Retrain that makes the  
processor read Line Probe Information (valid only in  
V.34 mode).  
$Rn  
n = 0 or 1  
n = 0 or 1  
*
*
$R0 means disconnect after 12 retransmits.  
$R1 means do not disconnect after 12 retransmits.  
&RFn  
Sr=n  
&RF0 selects CTS follows RTS.  
&RF1 selects CTS to act independently  
r = 0-11, 13,  
15-19, 24-26,  
29, 30, 32, 34...  
Sets value of Register “r” to value of “n”,  
where “n” is entered in Decimal format.  
* Factory Default Setting  
*** Not applicable in model MT2834BLK  
135  
 
MultiModemBL User Guide  
Command  
Values  
Description  
Sr?  
r = 0-11, 13,  
15-19, 24-26,  
30, 32 or 34...  
Reads value of Register “r” and displays  
value in 3-digit Decimal format.  
$SBn  
n = speed  
2834 and 1932 Series:  
$SB300 selects 300 bps at serial port.  
$SB1200 selects 1200 bps at serial port.  
$SB2400 selects 2400 bps at serial port.  
$SB4800 selects 4800 bps at serial port.  
$SB9600 selects 9600 bps at serial port.  
$SB19200 selects 19,200 bps at serial port.  
$SB38400 selects 38,400 bps at serial port.  
$SB57600 selects 57600 bps at serial port.  
$SB115200 selects 115200 bps at serial port.  
*
1432 Series:  
$SB300 selects 300 bps at serial port.  
$SB1200 selects 1200 bps at serial port.  
$SB2400 selects 2400 bps at serial port.  
$SB4800 selects 4800 bps at serial port.  
$SB9600 selects 9600 bps at serial port.  
$SB19200 selects 19,200 bps at serial port.  
$SB38400 selects 38,400 bps at serial port.  
$SB57600 selects 57600 bps at serial port.  
*
*
&SFn  
n = 0 or 1  
&SF0 selects DSR follows CD.  
&SF1 selects DSR independent.  
&Sn  
n = 0, 1 or 2  
&S0 forces Data Set Ready On.  
&S1 lets Data Set Ready act normally.  
&S2 Data Set Ready drop is regulated by S24 on  
disconnect.  
*
*
$SPn  
n = 0 or 1  
n = 4 or 5  
$SP0 disables UUCP Spoofing  
$SP1 enables UUCP Spoofing  
T
Modem will tone-dial numbers following the T.  
&Tn  
&T4 means Enable Response to Request for  
Remote Digital Loopback.  
*
*
&T5 means Disable Response to Request for  
Remote Digital Loopback.  
#Tn  
n = 0 or 1  
#T0 turns off Trellis Coded Modulation  
#T1 turns on Trellis Coded Modulation  
Un  
n = 0, 1, 2, or 3  
U0 places modem in Analog Loop Originate Mode.  
U1 places modem in Analog Loop Answer Mode.  
U2 places modem in Remote Digital Loopback test  
mode.  
U3 places modem in Local Digital Loopback test  
mode.  
$VDn  
n= 0 or 1  
*
$VD0 disables Voice/Data Dialing  
$VD1 enables Voice/Data Dialing  
* Factory Default Setting  
136  
 
Appendix D - AT Command Summary  
Command  
Values  
Description  
Vn  
n = 0 or 1  
V0 means Result Codes sent as digits (terse  
response).  
*
V1 means Result Codes sent as words (verbose  
response).  
W
Wait for new dial-tone.  
&Wn  
n = 0 or 1  
&W0 causes modem to store its current parameters  
in non-volatile RAM, and modem will load these for  
future sessions instead of reading factory ROM  
defaults, unless &F command used.  
*
*
&W1 causes modem to not store parameters.  
Xn  
n = 0,1,2,3 or 4  
X0 selects Basic Result Codes (w/o CONNECT  
1200, CONNECT 2400).  
X1 selects Extended Result Codes (w/CONNECT  
1200, CONNECT 2400).  
X2 selects Standard AT Command set with NO  
DIAL TONE.  
X3 selects Standard AT Command set with BUSY.  
X4 selects Standard AT Command set with NO  
DIAL TONE and BUSY.  
#Xn  
Yn  
Z
n= 0 or 1  
n = 0 or 1  
*
*
#X0 selects single XOFF character sent until XON  
level returns.  
#X1 selects multiple XOFF characters after buffer  
level is full.  
Y0 disables sending or responding to long space  
“break”.  
Y1 enables sending or responding to long space  
“breaks”.  
All configuration parameters are reset to default  
values.  
,
In Dial Command  
In Dial Command  
In Dial Command  
In Dial Command  
Causes pause during dialing.  
;
Causes return to Command Mode after dialing.  
Causes modem to flash On-Hook.  
!
@
Causes modem to wait for ringback, then 5 seconds  
of silence before processing next part of command.  
+++AT<CR>  
In-band Escape Sequence. Places modem in  
Command Mode while still remaining On-Line. Enter  
+++ followed by the letters A and T, up to ten  
command characters, and a RETURN.  
BREAK AT<CR>  
Out-of-band Escape Sequence. Places modem in  
Command mode while still remaining On- Line.  
Enter a BREAK signal, followed by the letters A and  
T, up to sixty command characters, and hit  
RETURN.  
* Factory Default Setting  
137  
 
MultiModemBL User Guide  
Callback Security/Remote Configuration Command Summary  
Command  
#DBn  
Description  
#DB0 disables Callback Security and answering Yes  
to the prompt turns off Callback Security and erases  
stored phone numbers and passwords. Answering  
No to the prompt aborts the command.  
#DB1 activates remote and local password security.  
#DB2 activates remote password security.  
#CBNyyxxxxxx  
Callback password with xxxxxx being callback  
password and yy being the memory location.  
Callback password xxxxxx must start with a non-  
numeric character and upper/lower case sensitive.  
Callback password xxxxxx must be a minimum of 6  
and maximum of 10 characters. yy memory  
locations are from 0 to 29. Must specify P (pulse) or  
T (tone) dialing in string.  
+ - Dxxxxxx???Nxx  
Callback Phone Numbers xxxxxx with the +  
preceding the phone number indicating the callback  
modem phone number for the corresponding  
password at the same memory location. The (-)  
preceding the phone number enables direct entry  
when the caller uses the correct password without  
the callback modem having to return the call. The  
??? entry at the end of the phone number  
represents an extension added to the main phone  
number. The Nxx is the memory location of the  
callback phone number and password.  
#Pn  
Parity of the prompt messages sent by the callback  
modem.  
#P0 is no parity  
#P1 is odd parity  
#P2 is even parity  
#RCBNxx  
#RDNxx  
Erases the callback password stored at memory  
location xx. Memory locations are 0 to 29.  
Erases the callback phone number stored at  
memory location xx. Memory locations are 0 to 29.  
138  
 
Appendix D - AT Command Summary  
Password Command Summary  
Command  
Description  
#Ixxxxxxxxxx  
Login Password is any keyboard characters (x)  
(upper/lower case sensitive), minimum 6 and  
maximum 10 characters. The default Login  
Password is #IMULTI-TECH.  
#Syyyyyyyyyy  
Setup Password is any keyboard characters (y)  
(upper/lower case sensitive), minimum 6 and  
maximum 10 characters. The default Setup  
Password is #SMODEMSETUP.  
V.25bis Commands  
Command  
Description  
$Vn  
$V0 returns modem to AT command mode when in  
V.25bis mode.  
$V1 enables V.25bis mode of operation.  
$V2 allows modem to receive one V.25bis command  
while in AT command mode without leaving AT  
command mode.  
$V5 DSR follows DTR in V.25bis mode.  
$V6 DSR does not follow DTR in V.25bis mode.  
Changes the serial bps rate.  
CSPs  
CSP0300 - 300 bps  
CSP1200 - 1200 bps  
CSP2400 - 2400 bps  
CSP4800 - 4800 bps  
CSP9600 - 9600 bps  
CSP19200 - 19200 bps  
CSP38400 - 38400 bps  
CSP57600 - 57600 bps  
CSP115200 - 115200 bps (1932 and 2834 models  
only)  
CRNdd  
Dials phone number dd where dd can be up to 20  
characters (0 through 9, *, #, P, T and :). Phone  
number is checked against the Delayed and  
Forbidden Number lists before dialed.  
CRIdd;nn  
DIC or CIC  
Dials dd same as CRN Command and ignores nn  
identification string. The disregard or connect to  
incoming calls commands are used for auto-answer  
operations.  
DIC stops the modem from answering incoming  
calls.  
CIC causes the modem to answer incoming calls.  
139  
 
MultiModemBL User Guide  
Appendix E - DIP-Switch Summary  
Asynchronous Mode  
DIP-Switch  
Condition  
Effect  
#1  
UP*  
Down  
DTR dependent on interface  
DTR forced On at all times  
#2  
UP*  
Down  
Hardware Flow Control  
Xon/Xoff Flow Control  
#3**  
2834 Series:  
UP  
Down*  
-15 dB Transmission (leased line)  
-9 dB Transmission (leased line)  
#3**  
1932 and 1432 Series:  
UP  
-10 dB Transmission (leased line)  
Down*  
0 dB Transmission (leased line)  
#4  
UP*  
Down  
UUCP Spoofing Off  
UUCP Spoofing On  
#5  
UP*  
Down  
Automatic Answer On  
Automatic Answer Off  
#6  
UP*  
Down  
Max throughput On  
Max throughput Off  
#7  
UP  
Down*  
RTS dependent on Interface  
RTS forced On at all times  
#8  
UP  
Down*  
Disable Command Mode  
Enable Command Mode  
#9  
UP  
Down*  
Local Digital Loopback On  
Remote Digital Loopback On  
#10  
#11  
#12  
UP*  
Down  
Dial-Up Operation  
Leased Line Operation  
UP  
Down*  
"AT" Responses  
Multi-Tech Responses  
UP  
Down*  
Synchronous Mode On  
Asynchronous Mode On  
*Factory Default Setting  
**Not applicable in BLK models  
140  
 
Appendix E - DIP-Switch Summary  
Synchronous Mode  
DIP-Switch  
Condition  
Effect  
#1  
UP*  
Down  
DTR Dependent On interface  
DTR forced On at all times  
#2  
UP*  
Down  
SDLC Mode On  
BSC Mode On  
#3  
UP  
Down*  
Command Mode Response Off  
Command Mode Response On  
#4  
UP*  
Down  
AS/400 Mode Off  
AS/400 Mode On  
#5  
UP*  
Down  
Answer Mode On  
Originate Mode On  
#6  
UP*  
Down  
Slave Clocking Off  
Slave Clocking On  
#7  
UP  
Down*  
RTS Dependent on interface  
RTS forced on at all times  
#8  
UP  
Down*  
Command Mode Off  
Command Mode On  
#9  
UP  
Down*  
Local Digital Loopback On  
Remote Digital Loopback On  
#10  
#11  
#12  
UP*  
Down  
Dial-Up Operation  
Leased Line Operation  
UP  
Down*  
External Clock selected  
Internal Clock selected  
UP  
Down*  
Synchronous Mode On  
Asynchronous Mode On  
*Factory Default Setting  
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MultiModemBL User Guide  
DIP Switches #13-14  
Note: The modem baud rate command ($MBn) overrides the setting of these speed selection  
switches (DIP switches #13 and #14).  
2834 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
1932 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
1432 Series:  
SWITCH  
#13/#14  
#13/#14  
#13/#14  
#13/#14  
CONDITION  
UP/UP*  
EFFECT  
28.8 K bps Operation  
19.2 K bps Operation  
14.4 K bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 9600 bps Operation  
CONDITION  
UP/UP*  
EFFECT  
19.2 K bps Operation  
14.4 K bps Operation  
9600 bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 2400 bps Operation  
CONDITION  
UP/UP*  
EFFECT  
14.4 K bps Operation  
9600 bps Operation  
4800 bps Operation  
DOWN/UP  
UP/DOWN  
DOWN/DOWN 2400 bps Operation  
DIP Switches #15-16  
#15  
#15  
#16  
#16  
UP*  
CD/DSR from Interface  
CD/DSR Forced On  
2-Wire Leased Line  
4-Wire Leased Line  
DOWN  
UP  
DOWN*  
*Standard Factory Default Setting  
142  
 
Appendix F - S-Register Summary  
Appendix F - S-Register Summary  
S-REGISTER UNIT  
RANGE  
DEFAULT  
DESCRIPTION  
S0  
1 ring  
0-255  
1
Sets number of rings before modem  
answers.  
S1  
1 ring  
ASCII  
0-255  
0-127  
0
Counts rings which have occurred.  
S2  
43  
Sets Escape Code character (default is plus  
+ sign).  
S3  
S4  
S5  
S6  
ASCII  
ASCII  
ASCII  
0-127  
13  
10  
8
Sets character recognized as RETURN  
(default is CTRL-M).  
0-127  
Sets character recognized as LINE FEED  
(default is CTRL-J).  
0-32,127  
Sets character recognized as BACKSPACE  
(default is CTRL-H).  
1 second 2-255  
4-255**  
2
4**  
4***  
Determines wait-time for  
dial tone.  
4-7***  
S7  
1 second 1-255  
1-45  
45  
55*  
Determines how long modem waits for  
carrier before aborting call.  
1-55*  
S8  
1 second 0-255  
4-255**  
2
4**  
4***  
Sets pause time caused by a comma  
character in a dial command.  
4-7***  
S9  
100 mSec 1-255  
100 mSec 1-255  
6
7
Sets carrier detect response time.  
S10  
Sets delay time between when carrier is lost  
and when modem disconnects.  
S11  
S13  
S15  
S16  
1 mSec  
ASCII  
Sec  
1-255  
80-255*  
70  
80*  
Sets time duration of and spacing between  
tones in tone-dialing.  
0-127  
37  
20  
Defines Remote Configuration Escape  
Character  
10-255  
Defines time delay for Callback attempts  
after initial passwords have exchanged.  
1 Attempt 1-255  
1-2***  
4
2***  
Defines the number of Callback attempts  
after initial passwords have exchanged  
between modems.  
S17  
10 mSec 0-2.5  
250 mSec  
30  
Defines length of break time (space) to PC.  
S18  
30 min  
10-255  
Defines how often leased-line is checked  
and restoral attempted.  
S19  
min  
0-255  
1
Timer used in dial backup mode. Specifies  
time duration modem attempts to restore  
leased line connection.  
* Values for International and DOC units only.  
** International only.  
*** Model MT2834BLK only.  
143  
 
MultiModemBL User Guide  
S-REGISTER UNIT  
RANGE  
50 mSec 0-255  
DEFAULT  
DESCRIPTION  
S24  
S25  
S26  
S29  
20  
Sets DSR/CTS/CD dropout time. Default  
(20) equals one second.  
100 mSec 0-255  
0
Sets DTR dropout time. 0 default equals 50  
mSec.  
1
1
0-255  
1-255  
0
Specifies number of failed password  
attempts allowed.  
20  
Specifies the amount of idle time can elapse  
between AT commands after the SETUP  
password has been entered  
S30  
min 0-255  
0
Inactivity timer used to disconnect modem.  
S32  
100mSec 0-255  
20  
Sets time that modem waits for a  
<RETURN> to be entered during escape  
sequence execution.  
S34  
ASCII  
0-60  
10  
Buffer size for number of characters in AT  
command string after on-line escape  
sequence, before buffer is cleared and  
escape sequence aborted.  
S36  
1 second 0-255  
1 second 0-255  
0
5
0
S36 sets the time between DTR inactive and  
the modem going off-hook (busy-out).  
S37  
S37 sets the time allowed DTR active and  
the modem responding on-hook (not busy).  
* S48  
N/A  
33, 31,  
S48 sets maximum speed modem connects  
within scope of Enhanced V34  
mode (e.g., S48 = 21 means  
28, 26, 24,  
21, 19, 16,  
14, 12, 96  
and 48  
maximum connect speed is  
21.6K). This register is useful when line  
conditions will not support higher V34  
speeds. The default value is 0, which  
indicates a connection attempt of 28.8K.  
lower speeds are still enabled.  
* 2834 Series only  
144  
 
Appendix G - Result Code Summary  
Appendix G - Result Code Summary  
TERSE (Digit)  
VERBOSE (Words)  
Effect  
0
OK  
Command was executed without error; ready for  
next command.  
1
2
3
CONNECT  
RING  
Modem has detected carrier and gone on-line.  
Modem has detected ring caused by incoming call.  
NO CARRIER  
No carrier signal has been detected within allowed  
time.  
4
5
ERROR  
Error in Command line (too many, or invalid  
characters).  
CONNECT 1200  
Modem has detected carrier at 1200 bps and gone  
on-line.  
6
7
8
9
NO DIAL TONE  
BUSY  
No dial tone has been detected.  
A busy signal has been detected.  
Remote system did not answer.  
NO ANSWER  
CONNECT 2400  
Modem has detected carrier at 2400 bps and gone  
on-line.  
11  
CONNECT 4800  
CONNECT 9600  
CONNECT 14400  
CONNECT 19200  
CONNECT 21600  
Modem has detected carrier at 4800 bps and gone  
on-line.  
12  
Modem has detected carrier at 9600 bps and gone  
on-line.  
13  
Modem has detected carrier at 14400 bps and gone  
on-line.  
19**  
21**  
Modem has detected carrier at 19200 bps and gone  
on-line.  
Modem has detected carrier at 21600 bps and gone  
on-line.  
23  
CONNECT 1275  
CONNECT 24000  
Modem is connected in V.23 mode.  
24*  
Modem has detected carrier at 24000 bps and gone  
on-line.  
26*  
28*  
31*  
33*  
CONNECT 26400  
CONNECT 28800  
CONNECT 31200  
CONNECT 33600  
Modem has detected carrier at 26400 bps and gone  
on-line.  
Modem has detected carrier at 28800 bps and gone  
on-line.  
Modem has detected carrier at 31200 bps and  
gone on-line.  
Modem has detected carrier at 33600 bps and  
gone on-line.  
* 2834 Series only  
** 1932 and 2834 Series only  
145  
 
MultiModemBL User Guide  
Note: If the modem is used in MNP Reliable mode, the following responses change:  
1R  
CONNECT RELIABLE  
5R  
9R  
CONNECT 1200 RELIABLE  
CONNECT 2400 RELIABLE  
CONNECT 4800 RELIABLE  
CONNECT 9600 RELIABLE  
CONNECT 14400 RELIABLE  
CONNECT 19200 RELIABLE  
CONNECT 21600 RELIABLE  
CONNECT 24000 RELIABLE  
CONNECT 26400 RELIABLE  
CONNECT 28800 RELIABLE  
CONNECT 31200 RELIABLE  
CONNECT 33600 RELIABLE  
11R  
12R  
13R  
19R**  
21R*  
24R*  
26R*  
28R*  
31R*  
33R*  
Note: If modem is used in LAP-M reliable mode, the following responses change:  
1L  
CONNECT LAPM  
5L  
9L  
CONNECT 1200 LAPM  
CONNECT 2400 LAPM  
CONNECT 4800 LAPM  
CONNECT 9600 LAPM  
CONNECT 14400 LAPM  
CONNECT 19200 LAPM  
CONNECT 21600 LAPM  
CONNECT 24000 LAPM  
CONNECT 26400 LAPM  
CONNECT 28800 LAPM  
CONNECT 31200 LAPM  
CONNECT 33600 LAPM  
10L  
12L  
13L  
19L**  
21L*  
24L*  
26L*  
28L*  
31L*  
33L*  
Note 1: If the modem is used with data compression, the word COMPRESSED or the letter C is  
added to result codes.  
Note 2: If the Standard AT Command Set 2400 responses are selected with the &Q command, the  
following responses change:  
9
(not used)  
10  
CONNECT 2400  
Modem has detected carrier at 2400 bps and  
gone on-line.  
* 2834 Series only  
** 1932 and 2834 Series only  
146  
 
Appendix H - V.25bis Operation  
Appendix H - V.25bis Operation  
Chapter 5 described a set of commands which let the modem dial, hang-up, and be configured for  
various applications. However, these commands, the AT command set, are only functional when the  
DTE transmits data asynchronously. That is, they cannot be used with synchronous equipment such  
as that found in IBM's Binary Synchronous Communications (BSC) and Synchronous Data Link  
Control (SDLC)* environments.  
The ITU V.25bis commands provide you with an alternate set of commands and responses to those  
described in Chapter 5 for applications in which the DTE is synchronous. V.25bis commands support  
dialing functions in asynchronous or synchronous mode according to the recommendations of the  
ITU; however, the AT commands are understood to reign in the asynchronous world, while the  
V.25bis commands are relegated to the synchronous world of datacomm. If you need to establish a  
datacomm link over Public Switched Telephone Network (PSTN) dial-up services, and your  
equipment outputs a synchronous data stream, V.25bis commands are essential. V.25bis mode AT  
commands do not include any modem configuration commands. You can execute normal AT  
commands in V.25bis mode for modem configuration.  
Delayed and Forbidden Numbers  
V.25bis provides the facility to delay failed call retry attempts by putting numbers that failed to  
connect on a special Delayed Number list. Subsequent dialing of these numbers will be delayed (time  
specified by a country regulation) and an appropriate message displayed. If the number is retried  
more than the maximum allowed number of times (number is also specified by country regulation), it  
is placed on the Forbidden Numbers list, and no further retries will be allowed. When the Forbidden  
Numbers list is full, no dialing is allowed and a CFIFF indication is given. The modem in AT command  
mode will respond with NO CARRIER. If country regulations require that the Forbidden Numbers list  
be checked in AT mode, then NO CARRIER will be the response to a dial attempt in AT mode.  
Numbers will also be put on the Forbidden Numbers list if the Delayed Numbers list is full and a new  
number fails for the first time. In that case, the new number will be added to the Delayed Number list  
and the oldest existing number added to the Forbidden Numbers list. Numbers are removed from the  
Forbidden Numbers list by after a certain time has past (also by country regulation).  
Some country regulations have numbers remain on the Forbidden Numbers list permanently. The  
Delayed Number and Forbidden Numbers lists are eight numbers long (20 characters each).  
V.25bis Operation  
Operation in V.25bis mode is similar to AT command mode in that certain DIP-Switch functions are  
important to its operation. V.25bis does not include any speed detection for asynchronous mode, so  
when you are giving commands, you must stay in your initial speed (i.e., if you change your terminal  
speed while entering an AT command, you will get no responses). In synchronous mode, the modem  
supplies the clock, so the synchronous terminal “knows” the speed.  
You must be in V.25bis mode for the commands described here to function. Most AT commands will  
also function, except those associated with dialing such as ATD, ATN, ATO, and ATU. To get into  
V.25bis mode, you type AT$V1. At this point your modem does no more speed or parity detection  
(things associated with asynchronous operation). To get out of V.25bis mode and back into AT  
command mode, enter AT$VO. The AT$V2 command allows you to run one V.25bis command from  
AT command mode without  
leaving AT command mode.  
There is no command to select between asynchronous and synchronous V.25bis operation. The  
position of DIP-Switch #12 selects between modes. For synchronous mode, DIP-Switch #12 must be  
UP, and the AT command mode enabled.  
147  
 
MultiModemBL User Guide  
Another asynchronous mode concern is the problem of connecting at a different speed than the  
speed at which the serial port is set. If your modem port speed is different from the serial port speed,  
you must either:  
1)  
2)  
Enable speed conversion and have flow control on, or  
Enable connect responses (with the ATX1 command) and change the serial baud rate  
after receiving a connect message.  
If the $VD1 command is entered when in Auto-Answer mode, the modem answers immediately upon  
receiving the first ring.  
There is no disconnect message (NO CARRIER) if a normal connection is made.  
V.25bis Set-Up and Initialization  
Before you operate your modem in the V.25bis mode, you need to make sure it is set up properly  
(various RS-232 lines such as DSR and CTS act as specified in the V.25bis standard). Setup  
involves proper DIP-Switch settings and soft-switches (software controlled conditions).  
V.25bis DIP-Switches  
#1  
#2  
#3  
#4  
#5  
#6  
Unforced DTR  
NA  
NA  
NA  
Auto-Answer enabled  
Async - Max throughput set  
Sync - Slave Clocking unforced  
#8  
Command Mode forced  
Digital Loopback Off  
#9  
#10  
#11  
#12  
Dial-Up  
Async - AT/Multi-Tech Resp.  
Async/Sync mode set per requirements  
148  
 
Appendix H - V.25bis Operation  
V.25bis Mode AT Commands  
The following commands will either alter standard V.25bis behavior (so you must be careful in their  
use) or they are not allowed, as indicated. All other commands can be used in V.25bis operation.  
A
Not Allowed  
A/  
Not Allowed  
A:  
Not Allowed  
D
Not Allowed  
D...N  
Not Allowed  
$D  
Alters Operation ($D1 in V25bis is direct call mode)  
E
Alters Operation  
&F  
Alters Operation (removes modem from asynchronous V.42bis mode)  
N
Not Allowed  
N...N  
Not Allowed  
O
Not Allowed  
P
Not Allowed  
T
Not Allowed  
U
Not Allowed  
W
Not Allowed  
X
Alters Operation (X0 no connect message, X1 connect message)  
,
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
Not Allowed  
;
!
@
+++AT<CR>  
V.25bis Responses (Result Codes)  
When in V.25bis mode (the AT$V1 command executed), your modem provides you with several  
responses which can help you follow the progress of V.25bis operations. These are similar to the  
Result Codes associated with AT Command mode operation. The V.25bis responses are in the form  
of three-character mnemonics as listed below:  
INC  
Incoming Call (same as RING indicator)  
A valid V.25bis command has been attempted  
Call delayed for t minutes (number on Delayed list)  
Call failure indicator where rr equals:  
VAL  
DLCt  
CFlrr  
et - Engaged tone (same as BUSY)  
nt - Call Answered but No Answer Tone  
ab - Call Not Answered  
fc - Number on Forbidden List  
ns - Number not stored in memory  
ua - User Abort  
nd - No Dialtone  
ff - Forbidden List full  
LSNmm;dd...dd  
LSDmm;dd...dd  
LSFmm;dd...dd  
CON ssss  
Phone number in V.25bis memory  
Phone number on the Delay list  
Phone number on the forbidden list  
Connection at ssss speed (if X1 in effect)  
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MultiModemBL User Guide  
V.25bis AT Commands  
The AT commands associated with V.25bis mode are described as follows. Note that one command  
enables and disables V.25bis mode and the rest are only operable in the V.25bis mode.  
Enable/Disable V.25bis Mode ($V) Command  
The function of the $V command is to select the V.25bis mode in asynchronous mode. (Synchronous  
mode is set up with switches. For example, the modem could be in AT command mode, (AT$V1),  
and if synchronous mode is enabled with AT Command mode enabled, then V.25bis mode is  
selected). Prior to executing this command, make sure that your modem is properly set up to perform  
the type of operation you will be performing. Refer to the initialization section of this appendix for  
information about modem set-up. When in V.25bis mode, most normal AT commands will also  
function (except D,N,O and U). V.25bis operates in asynchronous or synchronous modes (depending  
on the position of DIP-Switch #12), and does not check for terminal speed (so do not change speeds  
while in this mode) or parity. In synchronous mode, speed is not important since the internal clocks  
provide synchronization.  
To place your modem in V.25bis mode from asynchronous mode, enter the AT$V1 command. To  
return to AT command mode, enter the AT$V0 command. AT$V2 allows you to run one V.25bis  
command from AT command mode without leaving AT command mode (the V.25bis command  
follows $V2 on the command line).  
Change Serial Baud Rate (CSP) Command  
The CSP command will change the serial baud rate of your modem by entering CSPsssss where  
sssss can equal:  
0300  
1200  
2400  
4800  
9600  
=
=
=
=
=
300 bps  
1200 bps  
2400 bps  
4800 bps  
9600 bps  
19200 =  
38400 =  
57600 =  
115200 =  
19200 bps  
38400 bps  
57600 bps  
115200 bps (1932 and 2834 Series only)  
Dial Phone Number Provided (CRN) Command  
The CRN command permits the dialing of the phone number immediately following it (from the  
command line). It is similar to the D command of the AT command set, except that the number is first  
checked against the Delayed Number and Forbidden Number list. If permitted, depending on the  
country regulations in effect, the number will then be dialed. For example, if you enter CRN7859875  
and hit RETURN, your modem will check the two lists. If the number is on the Delayed Numbers list,  
you can dial that number again after t minutes have passed. If the number is on the Forbidden list, a  
CFIFC message will be displayed.  
You can use various commands from the AT command set within the CRN command line to facilitate  
the dialing process, such as P, T, or : for pulse dialing, tone dialing and wait for dial tone. V.25bis  
supports “smart” dialing.  
To dial a phone number, enter CRNdd...dd where dd...dd is the phone number, which can be up to  
20 characters long using any character on the telephone pad (0 through 9, *, #, P, T, and :).  
Some additional dialing characters may be available, based on country regulations.  
150  
 
Appendix H - V.25bis Operation  
Listing Delayed Phone Numbers (RLD) Command  
When a phone number is dialed by a CRN command and a connection is not made, the number is  
entered in the modem's V.25bis Delayed Number list along with the number of retry attempts. Any  
further dialing attempts will be delayed some amount of time (determined by the regulations of each  
country). While the delay is in progress, the modem will give a DLC indication. The list contains eight  
numbers. When filled, the next number failing “bumps” off the oldest number on the list onto the  
Forbidden Number list. Numbers on the Delayed Number list that succeed in a connect attempt are  
removed. If a certain number of failed attempts occur (the number of failed attempts is specified by  
each country), the number is entered into the V.25bis Forbidden Phone Number List. Forbidden  
phone numbers cannot be dialed at all. To list the phone numbers on the V.25bis Delayed Phone  
Number List, enter RLD and hit RETURN.  
Listing Forbidden Phone Number (RLF) Command  
Those phone numbers that have failed to connect the required number of times as specified by  
country regulations are removed from the Delayed Number list and entered onto the V.25bis  
Forbidden Number list. Numbers on the Forbidden Number list cannot be dialed at all for some  
maximum amount of time, which is also specified by country regulations. In some countries, the time  
might be one hour, and in others the number may never be dialed again. The forbidden list is eight  
numbers long, with the newest number replacing the oldest if the memory is full. To list the numbers  
in the Forbidden list enter RLF and hit RETURN.  
Disregard or Connect to Incoming Calls (DIC or CIC) Command  
The Disregard or Connect to Incoming Calls commands are used for Auto-Answer operations.  
Depending on the country regulations, your modem will wait some amount of time or number of rings  
before answering the call. During that time, you can stop the modem from answering the call by  
entering the DIC (Disregard Incoming Calls) command. The CIC (Connect to Incoming Calls)  
command will cause your modem to answer the call (either reversing the effect of a DIC command or  
simply have your modem answer the call immediately without waiting the regulation time before  
answering).  
DTR Dialing ($D) Command  
DTR Dialing is an alternate method of causing the modem to automatically dial a number. Data  
Terminal Ready (DTR) is a signal that comes into the modem from the terminal or computer to which  
it is connected via pin 20 of the RS-232 interface. In DTR Dialing, the modem will automatically dial a  
stored number as soon as it receives a high DTR signal. The DTR Dialing method is popular when  
using the modem in synchronous applications.  
To enable DTR Dialing, enter the command AT$D1 and hit Return. The modem will now dial the  
phone number you have stored as N0 when it receives a high DTR signal (see the D...N command in  
Chapter 5).  
DTR must remain high for the duration of the call, until disconnect. To disable DTR Dialing, enter the  
command AT$D0 (or AT$D) and hit RETURN.  
When you use DTR Dialing, be sure that DIP-Switch #1 is in the UP position, so that DTR is not  
forced on.  
In addition, when using DTR Dialing in a synchronous application, be sure that DIP-Switch #8 is in  
the UP position to disable V.25bis Command mode.  
151  
 
MultiModemBL User Guide  
ITU V.25bis Country Specific Information  
Due to the flexibility of the V.25bis standard, each country may establish specific regulations  
governing the way operations are handled. The purpose of this document is to detail each country's  
specific regulations that affect operation of V.25bis in Multi-Tech modems.  
1. Italy  
a)  
b)  
c)  
Command/Indicationmodifications  
1. Phone number indications include status ;ZPSTTT  
a)  
b)  
c)  
d)  
Z - U, D, or F, for Unrestricted, Delayed or Forbidden  
P - Delay time if delayed  
S - Number of retries so far  
TTT - Interdiction time to further attempts  
Delayed and Forbidden list behavior  
1.  
2.  
3.  
4.  
5.  
5 retries without delay  
2 minute delay between next 4 retries  
After 9 retries the number is put on the forbidden list  
120 minute timer is started on entry to delay list  
When it runs out, the number is removed from which ever list it is on  
Auto-Answer mode behavior  
1.  
2.  
3.  
Auto-Answer in 5 seconds if no DIC  
Get 10 seconds after DIC to enter CIC  
If 10 seconds times out then no connection is possible  
2. Switzerland  
a)  
Command/Indicationmodification  
1.  
2.  
3.  
4.  
Modem must remain on-hook for 5 seconds after disconnect  
Modem must remain on-hook for 5 minutes after 4 consecutive failed calls  
If modem must remain on-hook, then it is “paused”  
If the modem is paused and a call is attempted a PAU indication is given.  
a)  
Delayed and Forbidden list behavior  
PAUt Modem is paused for t minutes  
b)  
c)  
1.  
2.  
3.  
2 minute delay between 4 retries  
After 4 retries the number is put on the forbidden list  
The number remains on the forbidden list forever  
Auto-Answer behavior  
1.  
Auto-Answer mode after 2 rings if no DIC  
3.  
Austria  
a)  
b)  
Command/Indication modification (none)  
Delayed and Forbidden list behavior  
1.  
2.  
No delay between retries  
After 2 retries to numbers that answer, but give no answer tone (CFINT), the  
number is put on the forbidden list  
3.  
After 10 retries with busy or no dialtone, the number is put on the forbidden  
list  
4.  
5.  
The number remains on the forbidden list forever  
Delayed and Forbidden Numbers lists are checked when dialing in AT mode.  
If dialing is not possible then NO CARRIER is the response.  
c)  
Auto-Answer behavior  
1. Auto-Answer in 5 seconds if no DIC  
152  
 
Appendix H - V.25bis Operation  
4. France  
a)  
b)  
Command/Indication modification (none)  
Delay and Forbidden list behavior  
1.  
2.  
3.  
4.  
2 min. delay after 1st call, 4 after 2nd, 6 after 3rd, etc.  
After 5 retries, the number is put on the forbidden list  
The number remains on the forbidden list forever  
Delayed and Forbidden Numbers lists are checked when dialing in AT  
command mode. If dialing is not possible then No Carrier is the response.  
c)  
Auto-Answer mode behavior  
1.  
Auto-Answer in 5 seconds if no DIC  
5. Belgium  
a)  
b)  
Command/Indication modification (none)  
Delay and Forbidden list behavior  
1.  
2.  
3.  
1 min. delay between calls  
After 4 retries, the number is put on the forbidden list  
The number remains on the forbidden list for 1 hour after entry to forbidden  
list  
4.  
Delayed and Forbidden Numbers lists are checked when dialing in AT  
command mode. If dialing is not possible then No Carrier is the response.  
c)  
Auto-Answer behavior  
1.  
Auto-Answer in 5 seconds if no DIC.  
6. Singapore  
a)  
Command/indicationmodifications  
1.  
Dialing digit ‘=’ means wait for dialtone (acts the same as ‘:’ in dialing string).  
b)  
Delay and Forbidden list behavior  
1.  
2.  
3.  
4.  
5.  
5 retries without delay  
2 minute delay between next 4 retries  
After 9 retries the number is put on the forbidden list  
120 minute timer is started on entry to delay list  
When it runs out, the number is removed from whichever list it is on.  
153  
 
MultiModemBL User Guide  
Appendix I - MultiModemBL Cables  
These cables connect your modem to your terminal or computer’s serial port.  
25-PIN DTE  
Connector  
25-PIN DCE  
Device  
TD  
RD  
2
3
2
3
4
5
6
7
8
TD  
RD  
RTS 4  
CTS 5  
DSR 6  
GND7  
RTS  
CTS  
DSR  
GND  
CD  
CD  
8
DTR20  
RI 22  
20 DTR  
22 RI  
Figure I-1. RS232 Cable (IBM PC)  
1
2
3
4
5
6
RED (Tip)  
GREEN (Ring)  
To Terminal  
Block Screws  
(Transmit and Receive)  
RJ-11 Type  
Modular Plug  
Figure I-2. Two Wire Leased Line Connection  
RED  
3
TRANSMIT PAIR  
RECEIVE PAIR  
4
GREEN  
YELLOW  
2
5
BLACK  
To Terminal  
RJ-11 Type  
Modular Plug  
Block Screws  
(Transmit and Receive)  
Figure I-3. Four Wire Leased Line Connection  
154  
 
Appendix J - RS-232C Interface Specifications  
8 POS.  
MINI-DIN  
FEMALE  
8
7
6
5
4
3
2
1
25 POS  
MALE DSUB  
8 POS.  
MINI-DIN  
TD  
2
3
5
TD  
RCV3  
RCV  
RTS 4  
CTS 5  
GND7  
1
2
Handshake  
Out  
Handshake  
In  
4
8
GND  
GND  
Figure I-4. MAC Cable  
155  
 
MultiModemBL User Guide  
Appendix J - RS-232C Interface Specifications  
The modem's RS-232C interface circuits have been designed to meet the electrical specifications  
given in EIA (Electronic Industries Association) RS-232C standards. All signals generated by the  
modem are approximately 10 volts when measured across a load of 3000 ohms or greater. The  
receiving circuits of the modem will accept signals in the 3 to 25 volt range. The voltage thresholds  
are:  
Negative = voltage more negative than 3 volts with respect to signal ground  
Positive = voltage more positive than +3 volts with respect to signal ground  
SIGNAL INFORMATION:  
NEGATIVE  
POSITIVE  
Binary State  
Signal Condition  
Control and Timing Function  
One  
Mark  
Off  
Zero  
Space  
On  
The input impedances of all modem circuits which accept signals from the data processing terminal  
or CPU equipment have DC resistances of 4.7K. For more specific details, consult the EIA RS-232C  
standard itself.  
The following chart lists the EIA RS-232C interface pins and circuits present on the modem's  
RS232C Interface connector. All other pins are unused.  
Pin  
Assignment  
Designation eia  
circuit  
CCITT  
circuit  
signal  
Function  
source  
1
2
3
4
5
6
7
8
PG  
SD  
RD  
RTS  
CTS  
DSR  
SG  
CD  
+v  
HS  
TC  
RC  
TR****  
RI  
--  
101  
103  
104  
105  
106  
107  
102  
109  
--  
--  
Protective Ground  
Transmitted Data  
Received Data  
Request to Send  
Clear to Send  
Data Set Ready  
Signal Ground  
Carrier Detect  
Test Voltage  
BA  
BB  
CA  
CB  
CC  
AB  
CF  
+v  
DTE  
DCE  
DTE  
DCE  
DCE  
--  
DCE  
DCE  
DCE  
DCE  
DCE  
DTE  
DCE  
DTE  
DTE  
9**  
12  
15***  
17***  
20  
22  
24  
25  
--  
--  
High Speed  
DB  
DD  
CD  
CE  
DA  
CN  
114  
115  
108/2  
125  
113  
142  
Transmit Clock  
Receive Clock  
Terminal Ready  
Ring Indicator  
External Transmit Clock  
Terminal Busy  
XTC  
OOS  
** Pin 9 need not be present in your RS-232C cable  
*** Pins 15 and 17 are necessary only for synchronous operation  
**** Also known as DTR (Data Terminal Ready)  
The computer or terminal should be supplied with a cable terminated with a Cinch DB-25P (or  
equivalent) connector mounted in a Cinch DB-51226-1 (or equivalent) hood assembly as specified by  
the EIA RS-232C standard.  
156  
 
Appendix J - RS-232C Interface Specifications  
Functional Description of RS-232C Signals:  
Transmitted Data - Pin 2, SD (BA)  
Direction: to modem  
Signals on this circuit are generated by the customer's terminal and transferred to the transmitter of  
the modem. A positive signal is a space (binary 0) and a negative signal is a mark (binary 1). The  
transmitting terminal should hold this line in the marking state when no data is being transmitted,  
including intervals between characters or words. The TRANSMIT (XMT) LED indicates the status of  
this circuit.  
Received Data - Pin 3, RD (BB)  
Direction: from modem  
The lead is the data output of the modem. Data signals received from the remote modem are  
presented on this line. When no carrier signal is being received (pin 8 negative), this line will be  
forced into a marking condition. The RECEIVE (RCV) LED indicates the status of this signal.  
Request To Send - Pin 4, RTS (CA)  
Direction: to modem  
The RTS signal indicates to the modem that the computer or terminal has data that it wants to  
transmit.  
Clear To Send - Pin 5, CTS (CB)  
Direction: from modem  
The CTS line indicates to the terminal that the modem will transmit any data present on the Transmit  
Data line (pin 2).  
Data Set Ready - Pin 6, DSR (CC)  
Direction: from modem  
DSR On indicates that the modem is in the data mode and is connected to the communications  
channel. This signal will be on during analog-loop-test mode.  
Signal Ground - Pin 7, SG (AB)  
The SG lead is connected to signal ground of the modem. It establishes the common ground  
reference for all other interface signals.  
Data Carrier Detect - Pin 8, CD (CF)  
Direction: from modem  
DCD On (positive voltage) indicates that data carrier has been received from the other modem. This  
circuit will not normally turn on in the presence of message circuit noise or out-of-band signals. There  
is a one second delay between when the carrier tone has been detected and when the CD circuit is  
turned on.  
This signal goes off if received data carrier falls below the receiver threshold for more than 37 mSec.  
When CD is off, the Received Data circuit (pin 3) is held to the marking state.  
157  
 
MultiModemBL User Guide  
Test Voltage - Pin 9, XV  
Direction: from modem  
The XV lead has 330 ohms of resistance to +12 volts DC. This lead may be used to strap other  
signals high. For example, if the terminal does not supply a DTR (Data Terminal Ready) signal, Pin 9  
may be jumpered to Pin 20 (DTR) on the RS-232 connector or in the cable to force DTR on.  
Transmit Clock - Pin 15, TC (DB)  
Direction: from modem  
The TC signal is provided only when the modem is used in the synchronous mode. The clock is a  
square wave and is used to provide the computer or terminal with timing information for its Transmit  
Data circuit (pin 2). This clock will be provided on the interface at all times when the modem is in  
Synchronous mode.  
The first signal element of the Transmitted Data signal should be presented by the terminal on the  
first positive (Off to On) transition of TC which occurs after the CTS circuit on pin 5 has turned on.  
The transmitted data is sampled by the modem on negative transition  
of TC.  
Receive Clock - Pin 17, RC (DD)  
Direction: from modem  
The RC signal has the same characteristic of Transmit Clock, with the exception that it is used to  
provide the computer or terminal with timing information for its Receive Data (pin 3) circuit. The  
negative transition (On to Off) of RC indicates the center of each signal element on the Received  
Data circuit.  
Data Terminal Ready - Pin 20, TR or DTR (CD)  
Direction: to modem  
This signal (TR or DTR) provides a means for the terminal or computer to control the modem's  
connection to the communications channel. A high DTR signal is required by the modem to be able to  
communicate. Turning DTR off for more than 50 mSec will force the modem to disconnect.  
The most common use of DTR is in automatic answer applications. A high DTR signal is required by  
the modem to answer a call. A frequently used method is to have the computer turn on DTR in  
response to RI (Ring Indicator), which allows the modem to answer. Later, DTR is turned off at the  
conclusion of the log off procedure, which forces the modem to disconnect, enabling it to receive  
another call. In non auto answer applications it is advisable to leave DTR on using the modem's DIP-  
switch option. This is the standard factory setting. An alternative is to provide a constant high DTR  
from the terminal or computer. The Data Terminal Ready (DTR) LED indicates the status of this  
signal.  
Ring Indicator - Pin 22, RI (CE)  
Direction: from modem  
This signal will remain on for the duration of the ringing signal. When a ring signal is received by the  
modem, the modem will automatically answer after the first ring. The modem will answer after a  
specified number of rings which can be programmed in AT Command mode, but if none is specified,  
the modem will answer after the first ring.  
158  
 
Appendix J - RS-232C Interface Specifications  
External Transmit Clock - Pin 24, XTC  
Direction: to modem  
Supplies the same function as transmit clock on Pin 15.  
Terminal Busy (Out of Service) - Pin 25, OOS  
Direction: to modem  
The Terminal Busy (OOS) circuit is not defined in the RS-232C standard, but is used by us and most  
manufacturers to make the phone lines busy to incoming phone calls. Pin 25 is not normally  
connected to the RS-232C interface when shipped from the factory; it can be ordered connected as  
an option. If pin 25 is connected and is brought high, the modem will be placed Off Hook, and busy to  
incoming calls.  
159  
 
MultiModemBL User Guide  
Appendix K - Regulatory Information  
Compliance with BABT Requirements  
Approved for connection to telecommunications system specified in the instructions for use subject to  
the conditions set out in them.  
Warning: Interconnection directly, or by way of other apparatus, of ports marked "SAFETY  
WARNING see instructions for use" with ports marked or not so marked may produce hazardous  
conditions on the network. Advice should be obtained from a competent engineer before such a  
connection is made.  
This apparatus has been approved for the use of the following facilities:  
• Auto-calling  
• Loop disconnect and MF dialing  
• Phone number storage and retrieval by a predetermined code  
• Operation in the absence of proceed indication  
• Automatic storage of last number dialed  
• Tone detection-busy  
• Auto clear from the originating end  
• DTR dialing  
• Modem  
• PBX timed break register recall  
Compliance with BS6305 Clause 6.2, BS6320 Clause 7.2, and BABT/SITS/82/  
005S/D  
a. The modem is suitable for connection to the Public Switched Telephone Network (PSTN)  
provided by British Telecommunications plc or Kingston Communications (Hull) plc. Circuit  
supply by British Communications, Mercury Communication, or Hull City Council. Only direct  
exchange lines may be used, not shared service.  
b. The modem is suitable for household, office, and similar general indoor use. It is not suitable for  
use as an extension to a payphone.  
c. BT lines supplied must support either loop disconnect or multifrequency tone signalling.  
d. REN (Ringer Equivalence Number).  
The REN value of a unit is calculated from 3/n where n is the total number of units which can be  
connected in parallel which will still cause the standard bell (as defined in BS6305 Appendix D) to  
ring.  
REN values of less than 0.3 cannot be assigned.  
REN = 1  
If a telephone or other device is connected in parallel with the modem, the combined REN must not  
exceed 4. A BT supplied telephone may be assumed to have REN of 1.0 unless otherwise noted.  
The approval of this modem for connection to the British Telecom public switched telephone network  
is INVALIDATED if the apparatus is subject to any modification in any material way not authorized by  
BABT or if it is used with or connected to:  
i. internal software that has not been formally accepted BABT.  
ii. external control software or external control apparatus which cause the operation of the modem  
associated call set-up equipment to contravene the requirements of the standard set out in  
BABT/SITS/82/005S/D.  
160  
 
Appendix K - Regulatory Information  
All other apparatus connected to this modem and thereby connected directly or indirectly to the  
British Telecom public switched telephone network must be approved apparatus as defined in  
Section 22 of the British Telecommunications Act 1984.  
The Approval Label is as follows:  
APPROVED for connection to  
telecommunications systems specified  
in the instruction for use subject to  
conditions set out in them  
The REN number for this apparatus = 1  
Compliance with European Community Requirements  
EMC, Safety and Terminal Directive Compliance  
The CE mark is affixed to this product to confirm compliance with the following European Community  
Directives:  
Council Directive 89/336/EEC of 3 May 1989 on the approximation of the laws of Member States  
relating to electromagnetic compatibility.  
and  
Council Directive 73/23/EEC of 19 February 1973 on the harmonization of the laws of Member States  
relating to electrical equipment designed for use within certain voltage limits:  
and  
Council Directive 98/13/EC of 12 March 1998 on the approximation of the laws of Member States  
concerning telecommunications and Satellite earth station equipment.  
European Directives User Guide Statement  
Note: The following statement applies only to products marked with Pan-European approval  
markings.  
The equipment has been approved to [Commission Decision “CTR21”] for pan-European single  
terminal connection to the Public Switched Telephone Network (PSTN). However, due to differences  
between the individual PSTNs provided in different countries, the approval does not, of itself, give an  
unconditional assurance of successful operation on every PSTN network termination point. In the  
event of problems, you should contact your equipment supplier in the first instance.  
This equipment is designed to work with PSTN networks that accept analog signals. Multi-Tech does  
not currently know of any interoperating difficulties.  
161  
 
MultiModemBL User Guide  
International Modem Restrictions  
Some dialing and answering defaults and restrictions may vary for international modems. Changing  
settings may cause a modem to become non-compliant with national telecom requirements in  
specific countries. Also note that some software packages may have features or lack restrictions that  
may cause the modem to become non-compliant.  
New Zealand Telecom Warning Notice  
Use of pulse dialing, when this equipment is connected to the same line as other equipment, may  
give rise to ‘bell tinkle’ or noise and may also cause a false answer condition. Should such problems  
occur, the user should NOT contact the Telecom Faults Service. The preferred method of dialing is to  
use DTMF tones, as this is faster than pulse (decadic) dialing and is readily available on almost all  
New Zealand telephone exchanges.  
Warning Notice: No ‘111’ or other calls can be made from this device during a mains power failure.  
162  
 
Appendix K - Regulatory Information  
FCC Regulations for Telephone Line Interconnection  
1. This equipment complies with Part 68 of the Federal Communications Commission (FCC) rules.  
On the outside surface of this equipment is a label that contains, among other information, the  
FCC registration number and ringer equivalence number (REN). If requested, this information  
must be provided to the telephone company.  
2. As indicated below, the suitable jack (Universal Service Order Code connecting arrangement) for  
this equipment is shown. If applicable, the facility interface codes (FIC) and service order codes  
(SOC) are shown.An FCC-compliant telephone cord and modular plug is provided with this  
equipment. This equipment is designed to be connected to the telephone network or premises  
wiring using a compatible modular jack which is Part 68 compliant. See installation instructions  
for details.  
3. The ringer equivalence number (REN) is used to determine the quantity of devices which may be  
connected to the telephone line. Excessive REN’s on the telephone line may result in the devices  
not ringing in response to an incoming call. In most, but not all areas, the sum of the REN’s  
should not exceed five (5.0). To be certain of the number of devices that may be connected to  
the line, as determined by the total REN’s, contact the telephone company to determine the  
maximum REN for the calling area.  
4. If this equipment causes harm to the telephone network, the telephone company will notify you in  
advance. But if advance notice isn’t practical, the telephone company will notify the customer as  
soon as possible. Also, you will be advised of your right to file a complaint with the FCC if you  
believe it is necessary.  
5. The telephone company may make changes in its facilities, equipment, operations, or procedures  
that could affect the operation of the equipment. If this happens, the telephone company will  
provide advance notice in order for you to make necessary modifications in order to maintain  
uninterrupted service.  
6. If trouble is experienced with this equipment (the model of which is indicated below) please  
contact Multi-Tech Systems, Inc. at the address shown below for details of how to have repairs  
made. If the trouble is causing harm to the telephone network, the telephone company may  
request you remove the equipment from the network until the problem is resolved.  
7. No repairs are to be made by you. Repairs are to be made only by Multi-Tech Systems or its  
licensees. Unauthorized repairs void registration and warranty.  
8. This equipment cannot be used on public coin service provided by the telephone company.  
Connection to Party Line Service is subject to state tariffs. (Contact the state public utility  
commission, public service commission or corporation commission for information.)  
9. If so required, this equipment is hearing-aid compatible.  
Trade Name:  
MultiModemIITM  
Model Number:  
FCC Registration #:  
MT2834BL, MT1932BL, MT1432BL  
AU7USA-20673-MM-E (2834 Series)  
AU7USA-75640-MM-E (1932 Series)  
AU7USA-73205-FA-E (1432 Series)  
0.3B (2834 Series)  
Ringer Equivalence:  
0.8B (1932 and 1432 Series)  
RJ11C or RJ11W (single line)  
Multi-Tech Systems, Inc.  
Modular Jack (USOC):  
Service Center in USA:  
2205 Woodale Drive  
Mounds View, Minnesota 55112 U.S.A.  
(612) 785-3500 or (800) 328-9717  
U. S. FAX 612-785-9874  
Fax-Back Service (612) 717-5888  
Technical Support (800) 972-2439  
BBS (612) 785-3702 or (800) 392-2432  
Internet Address: http://www.multitech.com  
163  
 
MultiModemBL User Guide  
Canadian Limitations Notice  
Notice: The ringer equivalence number (REN) assigned to each terminal device provides an  
indication of the maximum number of terminals allowed to be connected to a telephone interface. The  
termination of a interface may consist of any combination of devices subject only to the requirement  
that the sum of the ringer equivalence numbers of all the devices does not exceed 5.  
Notice: The Industry Canada label identifies certificated equipment. This certification means that the  
equipment meets certain telecommunications network protective, operational and safety  
requirements. The Industry Canada does not guarantee the equipment will operate to the user’s  
satisfaction.  
Before installing this equipment, users should ensure that it is permissible to be connected to the  
facilities of the local telecommunications company. The equipment must also be installed using an  
acceptable method of connection. The customer should be aware that compliance with the above  
conditions may not prevent degradation of service in some situations.  
Repairs to certified equipment should be made by an authorized Canadian maintenance facility  
designated by the supplier. Any repairs or alterations made by the user to this equipment, or  
equipment malfunctions, may give the telecommunications company cause to request the user to  
disconnect the equipment.  
Users should ensure for their own protection that the electrical ground connections of the power  
utility, telephone lines and internal metallic water pipe system, if present, are connected together.  
This precaution may be particularly important in rural areas.  
Caution: Users should not attempt to make such connections themselves, but should contact the  
appropriate electric inspection authority, or electrician, as appropriate.  
Class A Statement  
FCC Part 15  
This equipment has been tested and found to comply with the limits for a Class A digital device,  
pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection  
against harmful interference when the equipment is operated in a commercial environment. This  
equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in  
accordance with the instruction manual, may cause harmful interference to radio communications.  
Operation of this equipment in a residential area is likely to cause harmful interference in which case  
the user will be required to correct the interference at his own expense.  
This device complies with Part 15 of the FCC rules.  
Operation is subject to the following two conditions:  
(1)  
(2)  
This device may not cause harmful interference.  
This device must accept any interference that may cause undesired operation.  
Warning: Changes or modifications to this unit not expressly approved by the party responsible for  
compliance could void the user’s authority to operate the equipment.  
Industry Canada  
This Class A digital apparatus meets all requirements of the Canadian Interference-Causing  
Equipment Regulations.  
Cet appareil numerique de la classe A respecte toutes les exigences du Reglement sur le materiel  
brouilleur du Canada.  
164  
 
Index  
Callback Security Enable/Disable (#DB) ............93  
Index  
Callback Time Delay ................................... 81, 95  
"Calling Card" Detect Tones ($).........................52  
Carrier Detect Control (&C) ................................61  
Carrier Detect Response Time ...........................80  
Carrier Detect/DSR Forcing ............................. 114  
Carrier Frequencies ...........................................14  
Carrier Loss Disconnect Delay Time ..................80  
Change LOGIN Password (#I) ...........................93  
Change Serial Baud Rate (CSP) Command ....150  
Change SETUP Password (#S) .........................93  
Changing Break Time .........................................81  
Clear To Send...................................................157  
Cleardown at Disconnect ...................................59  
COM ports  
COM2 ...................................................... 29, 31  
COMM.DRV ..................................... 29, 127, 128  
Command Buffer ................................................13  
"Command mode" ..............................................43  
Command string .................................................30  
Command Summary ........................................131  
Commands  
Attention code.................................................29  
Auto-Reliable mode ........................................32  
Data compression...........................................32  
Load default configuration ..............................30  
Modem reset...................................................29  
Non-Error Correction mode ............................32  
Reliable mode .................................................32  
Compatibility.......................................................12  
CompuServe ........................................ 28, 29, 32  
CompuServe/Internet .......................................121  
Computer-or Terminal-Initiated Flow Control (Pacin  
69  
Symbols  
&E0 ....................................................................32  
&E1 ....................................................................32  
&E14 ..................................................................32  
&T command ....................................................101  
16550 UART and Windows 3.1 ..........................29  
2 Wire/ 4 Wire Operation.................................. 114  
2 Wire/4 Wire Operation................................... 114  
A
Abort Timer.........................................................79  
Accessories......................................................122  
AGC Dynamic Range .........................................15  
Answer Mode .....................................................64  
Answer/Originate - Voice/Data Toggle Switch ....33  
AS/400 Mode ................................................... 110  
ASCII code .........................................................30  
Assign Passwords Callback Phone for Numbers  
(#CBN) ...............................................................93  
Asynchronous Word Lenth Selection ($EB) .......68  
Asynchronous/Synchronous Operation............ 113  
AT .......................................................................29  
AT Command and S-Register Summary ............86  
AT Commands....................................................44  
"AT" Responses/Multi-Tech Responses ........... 113  
Auto-answer ................................................ 30, 31  
Auto-Reliable Buffering ($A)...............................64  
Auto-Reliable Mode (&E1)..................................63  
B
Backspace Character .........................................79  
Basic Result Code..............................................57  
Basic/Extended Result Codes............................57  
Baud Adjust ($BA) ..............................................70  
Baud rate  
Serial port .......................................................31  
BBS ..................................................................120  
Bell/V.21 Tone ....................................................58  
BREAK AT<CR> ................................................74  
British Telecom .................................................160  
British Telecommunications pic ........................160  
Buffer Length of Command Mode...After On-line  
Esca ...................................................................83  
Bulletin board systems ......................... 29, 31, 32  
Connectors .........................................................15  
Continuous Redial (A or :) ..................................49  
Controls ..............................................................15  
CTS Control (&R) ...............................................61  
CTS signal..........................................................31  
CTS/RTS Interaction Control (&RF) ...................62  
CYBERC.ZIP......................................................29  
D
Data Carrier Detect ..........................................157  
Data Compression ...................................... 13, 32  
Data Compression Commands ..........................69  
Data Format .......................................................12  
Data Rates .........................................................12  
Data Set Ready ................................................157  
Data Set Ready Control (&S) .............................61  
Data Terminal Ready ........................................158  
Data Terminal Ready Control (&D) .....................61  
Datacomm software ....... 28, 29, 30, 31, 32, 124  
Configuration ........................................... 29, 31  
dB Transmission Levels ................................... 110  
Delayed and Forbidden Numbers ....................147  
C
Call waiting .......................................................127  
Callback Attempts ..............................................81  
Callback Operational Sequence Procedures .....91  
Callback Password and Dial Back Phone Number  
Entry ...................................................................90  
Callback Retry Attempts .....................................95  
165  
 
MultiModemBL User Guide  
Diagnostics.........................................................15  
Dial (D) ...............................................................49  
Dial Phone Number Provided (CRN) Command150  
Dial Pulse and Tone-Dial Frequencies .............130  
Dialing a Stored Number (N) ..............................49  
Dialing/On-Line/Answering .................................28  
Digital Loopback Test ................................ 98, 112  
Dimensions ........................................................15  
DIP-Switch Summary .......................................140  
DIP-Switches.................................................... 115  
Disregard or Connect to Incoming Calls (DIC or CIC  
151  
Force Answer Mode (A) .....................................75  
Forced DTR......................................................109  
Four Wire Leased Line Connection ..................154  
Frequency Stability.............................................14  
Front panel .......................................................124  
FUNCTIONAL DESCRIPTION OF RS232C SIG-  
NALS ................................................................157  
Functional States ...............................................43  
G
Garbage Characters.........................................128  
Guard Tones (&G) ..............................................58  
DSR/CD Interaction Control (&SF).....................62  
DTR Dialing ($D) ................................................49  
DTR Dialing ($D) Command ............................151  
DTR Dropout Time .............................................82  
DTR signal .........................................................31  
Dual-Tone Multi-Frequency dialing .....................50  
“dumb” dialing.....................................................57  
H
"handshake" .......................................................37  
Hardware Flow Control (&E4) ............................66  
Help Screens ($H)..............................................73  
HOW TO ................................................................  
COMMANDS ......................................................44  
E
I
echnical Specifications .......................................12  
Enable/Disable Auto-Answer............................ 111  
Enable/Disable Auto-Reliable Fallback Character65  
Enable/Disable Command Mode..................... 112  
Enable/Disable V.25bis Mode ($V) Command .150  
Enable/Suppress Responses ...........................109  
Erase Callback Password (#RCBNxx) ...............94  
Erase Callback Phone Number (#RDNxx) .........94  
Error Correction........................................... 12, 32  
Error correction ..................................................32  
Escape Code Character .....................................78  
Escape Sequence Options (%E)........................74  
Escape Sequences (+++AT<CR>).....................74  
European Low Voltage Directive ......................161  
Examples of Assigning Values ...........................85  
Examples of Reading Values .............................85  
Exiting Command Mode, Going Back On-Line (O)75  
Extended Result Codes .....................................57  
External Transmit Clock ...................................159  
Immediate Action Line Probe Commands ..........75  
Inactivity Timer ............................................ 82, 83  
Indicators............................................................15  
Initialization strings ....... 29, 30, 31, 32, 124, 126  
Macintosh .......................................................31  
PC-compatible ................................................30  
initiating Line Probe ............................................75  
Intelligent Features.............................................13  
Intelligent Serial Interface (ISI) ...........................72  
Interface .............................................................15  
Internal/External Clocking ................................ 113  
K
Kingston Communications (Hull) pic ................160  
L
Lease Line Restoral ...........................................14  
Leased Line/Dial-Up Operation ........................ 112  
Limited Warranty ....................................... 15, 118  
Line Feed Character...........................................79  
“Link Request” ....................................................63  
Listing Current Operating Parameters (L5 L7) ..73  
Listing Delayed Phone Numbers (RLD) Command  
151  
F
Failed Password Attempts..................................95  
“fallback.............................................................59  
Fallback Modes When On-Line (#F) ..................59  
Fax .....................................................................30  
Fax and Communications Software Won't Run 128  
Fax Carrier Frequencies ....................................14  
Fax Modulations .................................................13  
Fax-Back Service .............................................121  
File transfer protocols.........................................32  
Flash On Hook (!) ...............................................51  
FlashPro to Upgrade Modem Firmware ...........121  
Flow Control .....................................................109  
Flow control ............................................... 31, 128  
Flow Control - &E4/&E5 ...................................109  
Listing Forbidden Phone Number (RLF) Command  
151  
Listing Numbers Stored in Memory (L)...............53  
Listing On-Line Diagnostics (L8) ........................74  
Listing S-Register Values (L6) ............................73  
Loading Factory Defaults (&F) ...........................54  
Local Analog Loopback Test...............................98  
Local Inactivity Timer..........................................95  
Long Space Disconnect (Y) ...............................51  
Losing Data ......................................................128  
166  
 
Index  
M
Q
MAC Cable .......................................................155  
Macintosh computer .................................... 28, 31  
Maximum Throughput Setting .......................... 111  
Memory  
Quiet Answer (@) ...............................................52  
R
Reading of Line Probe Information Commands .75  
Receive Clock ..................................................158  
Received Data..................................................157  
Receiver Sensitivity ............................................15  
Reliable Mode (&E2) ..........................................63  
Remote Configuration Character........................95  
Remote Configuration Escape Character...........80  
Remote Configuration Procedures .....................92  
Remote System Configuration ...........................31  
Request To Send ..............................................157  
Request To Send Forced.................................. 112  
Result Code Summary .....................................145  
Result codes ............................................. 30, 126  
Result Codes Enable/Disable and No Response (Q)  
56  
Nonvolatile (NVRAM) .....................................30  
MNP 5 ....................................................... 32, 127  
Model Numbers ..................................................12  
Modem Baud Rate ($MB)...................................70  
Modem Cannot Connect When Answering ......127  
Modem Dials But Cannot Make a Connection..126  
Modem Disconnects While Online ...................127  
Modem Does Not Respond to Commands.......124  
Modem Reset (Z) ...............................................54  
Modem-Initiated Flow Control Commands .........69  
Modulation..........................................................13  
MSD.EXE ...........................................................28  
MT1432BL Connections .............................. 22, 23  
MT2834BL Cables............................................154  
Result Codes Verbose/Terse (V) ........................56  
Retransmit Count ($R) .......................................65  
Return Character................................................78  
Return character ................................................30  
Return to Command Mode After Dial Execution (;)51  
Reverse the Mode of Operation (R) ...................51  
Ring Indicator ...................................................158  
Ringer Equivalence Number ............................160  
Rings Which Have Occurred ..............................78  
RS232 Cable ....................................................154  
RS232 Cable (IBM PC) ....................................154  
RS232C Interface Specifications......................156  
RTS signal..........................................................31  
N
noise information ................................................75  
Normal Mode (&E0) ...........................................63  
Normal Mode Modem Flow Control (&E11) ........68  
Normal/Auto-Reliable/Reliable Mode Commands69  
Number Linking (NN) .........................................53  
Number of Rings Until Modem Answers...... 78, 84  
O
"On-line mode" ...................................................43  
On-line Warranty Registration .......................... 118  
Ordering Accessories .......................................122  
Originate Mode...................................................64  
Originate/Answer Mode .................................... 111  
S
S-Register Summary ........................................143  
S-Registers  
P
S3 ...................................................................30  
SCC....................................................................28  
SDLC/BSC Option............................................109  
Send Xon/Xoff Characters (#X) ..........................67  
Serial cable ............................................... 31, 125  
Serial port ..................... 28, 29, 31, 32, 125, 128  
Serial Port Baud Rate ($SB) ..............................72  
serial ports..........................................................72  
Sessions.............................................................29  
Set Pulse Dial Ratios (&P) .................................50  
Signal Ground ..................................................157  
SIGNAL INFORMATION ..................................156  
Signal Strength information ................................75  
Signal to Noise Ratio information (SNR) ............75  
SIT files ..............................................................32  
Slave Clocking ................................................. 111  
Slow File Transfer ............................................127  
smart dialing .......................................................57  
Speaker ..............................................................15  
Pacing ................................................................31  
Parameters........................................... 29, 30, 31  
Changing defaults ...........................................30  
Defaults ..........................................................30  
Parity ..................................................................29  
Parity Selection (#P) ..........................................68  
Password Command Summary ......................139  
Pause Time for Comma......................................79  
PBX/CBX Disconnect Drop Time for DSR/CTS/CD82  
PBX/CBX systems .............................................82  
Power .................................................................15  
Power supply....................................................124  
Program V.34bis Connect Speeds .....................84  
Program V34 Connect Speeds...........................84  
Protocols ................................................... 32, 127  
Pulse or Tone Dial (P T) ....................................50  
167  
 
MultiModemBL User Guide  
Speed Conversion ($BA) ...................................70  
Speed Switches ............................................... 113  
Storing Phone Numbers (D...N) .........................53  
Summary ............................................................86  
Synchronous Transmit Clock Select (&X) ..........55  
serial port driver ................................... 127, 128  
Windows 95 Autodetect Inquiry Command (I9) ..73  
Windows 95 HyperTerminal..............................127  
X
Xmodem ...........................................................127  
XON/XOFF .........................................................31  
Xon/Xoff Flow Control (&E5) ..............................66  
Xon/Xoff Pass-Through (&E7)............................67  
Xon/Xoff Pass-Through Commands...................69  
T
Telephone line ..................................................126  
Terminal Busy (Out of Service) ........................159  
Terminal mode..................................................124  
Terminal/Computer Initiated Pacing (&E13) .......68  
Test Voltage......................................................158  
Testing ..................................................... 124, 126  
self-test .........................................................124  
Time Elapse for Escape Sequence ....................83  
Time for Carrier (Abort Timer) ............................79  
Tone Dialing: Tone Spacing and Duration ..........80  
Tradename .........................................................12  
Transmission speed .................................... 28, 31  
Transmit Clock .................................................158  
Transmit Level ....................................................14  
Two Wire Leased Line Connection...................154  
Y
Ymodem/G .......................................................127  
Z
ZIP files ..............................................................32  
Zmodem ...........................................................127  
U
UART .......................................................... 28, 72  
UARTs ...................................28, 29, 31, 32, 128  
16450................................................ 28, 29, 31  
16550...............................28, 29, 31, 127, 128  
8250......................................................... 28, 31  
8250A ............................................... 28, 29, 31  
Buffers ............................................................29  
Identifying .......................................................28  
Unix UUCP Spoofing ........................................ 110  
Unix UUCP Spoofing ($SP)................................55  
Upgrading the MT2834BL ................................121  
V
V.25bis Mode AT Commands ..........................149  
V.25bis AT Commands .....................................150  
V.25bis Operation .............................................147  
V.25bis Responses (Result Codes)..................149  
V.25bis Set-Up and Initialization .......................148  
V.42 ....................................................................32  
V.42 Mode Select (#L) ........................................64  
V.42bis.................................................. 28, 31, 32  
W
Wait for New-Dial-Tone (W)................................51  
Wait Time for Dial Tone ......................................79  
"Wait-for-Carrier" ................................................43  
Warranty........................................................... 118  
On-line Registration ...................................... 118  
Weight ................................................................15  
Windows 3.1..................................... 29, 127, 128  
Serial port driver .............................................29  
168  
 

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