Multitech BA-Series User manual

BA-Series
Intelligent Data/Fax Modem
User Guide

User Guide
88312001 Revision B
MultiModemIIModels:
MT2834BA/MT2834BAI
This publication may not be reproduced, in whole or in part, without prior expressed written
permission from Multi-Tech Systems, Inc.
All rights reserved.
Copyright 1999-2002 ©, by Multi-Tech Systems, Inc.
Multi-Tech Systems, Inc. makes no representations or warranties with respect to the contents hereof
and specifically disclaims any implied warranties of merchantability or fitness for any particular
purpose. Furthermore, Multi-Tech Systems, Inc. reserves the right to revise this publication and to
make changes from time to time in the content hereof without obligation of Multi-Tech Systems, Inc.
to notify any person or organization of such revisions or changes.
Record of Revisions
A (06/01/99) Manual revised. Manual reformatted for electronic distribution. All
pages remain at Revision A.
B(08/15/02) Replace Trio with PhoneTools; change phone numbers; add patents;
revised safety warnings
Trademarks of Multi-Tech Systems, Inc. are as follows:
MultiModemII, Multi-Tech and the Multi-Tech logo.
MNP, Microcom Network Protocol is a trademark of Microcom Inc.
AS/400 and System3x is a trademark of IBM.
Macintosh is a trademark of Apple Computer Inc.
Unix is a trademark of X/Open Co. Ltd.
Windows® is a registered trademarks of Microsoft
All other brands and product names mentioned in this publication are trademarks or registered
trademarks of their respective companies.
Multi-Tech Systems, Inc.
2205 Woodale Drive
Mounds View, Minnesota 55112 U.S.A.
[phone] or [phone]
U. S. Fax [phone]
Technical Support [phone]
Internet Address: http://www.multitech.com

Contents
Chapter 1 - Introduction and Description......................................................................... 5
1.1 Introduction...................................................................................................................................... 6
1.2 How To Use This Manual................................................................................................................. 6
1.3 Modem Features ............................................................................................................................. 7
1.3.1 2834 Series Features................................................................................................................ 8
1.4 Fax Features ................................................................................................................................... 8
1.5 Technical Specifications .................................................................................................................. 9
1.6 Power .............................................................................................................................................. 10
1.7 Modem LED Indicators .................................................................................................................... 11
1.8 Controls on PC Board ..................................................................................................................... 12
Chapter 2 - Installation and Connection......................................................................... 13
2.1 What is in Your Modem Package? .................................................................................................. 14
2.2 Installation ....................................................................................................................................... 14
2.2.1 Safety Warnings ........................................................................................................................ 15
2.2.2 Installation Procedure ............................................................................................................... 15
2.3 Installing Data Communications Software ....................................................................................... 16
Chapter 3 - Software Configuration and Modem Basics .............................................. 17
3.1 Introduction...................................................................................................................................... 18
3.2 Configuring Your Software............................................................................................................... 18
3.2.1 ConfiguringSoftware for Your Modem ....................................................................................... 18
3.4 PC Initialization Strings ................................................................................................................... 18
3.4.1 Changing Default Parameters................................................................................................... 19
3.4.2 Other Parameters ..................................................................................................................... 19
3.5 Configuring Software for Your Computer ......................................................................................... 19
3.5.1 Configuring Software for the Remote System........................................................................... 19
3.5.2 Terminal Emulation ................................................................................................................... 20
3.5.3 File Transfer Protocols .............................................................................................................. 20
Chapter 4 - Command Mode............................................................................................ 21
4.1 Introduction...................................................................................................................................... 22
4.1.1 AT Command Editing ................................................................................................................ 22
4.1.2 Functional Modes...................................................................................................................... 22
4.2 Summary of AT Commands............................................................................................................. 23
4.3 Result Codes ................................................................................................................................... 26
4.4 Dialing Commands .......................................................................................................................... 27
4.4.1 Dialing Action Commands ......................................................................................................... 27
4.4.2 Dial Modifier Commands........................................................................................................... 28
4.4.3 Phone Number Memory Commands......................................................................................... 30
4.4.4 Configuration and Default Storage Commands ........................................................................ 31
4.4.5 Command Response (Result Code) Commands ...................................................................... 33
4.4.6 Phone Line Conditioning Commands........................................................................................ 34
4.4.7 RS-232C Interface Control Commands .................................................................................... 36
4.4.8 Error Correction Commands ..................................................................................................... 38
4.4.9 Flow Control Commands .......................................................................................................... 40
4.4.10 Compression, Error Correction, Flow Control, Pass-Through and Pacing Commands ............ 43
4.4.11 Speed Conversion Commands ................................................................................................. 44
4.4.12 Immediate Action Commands ................................................................................................... 46
4.4.13 Line Probe Commands ............................................................................................................. 48

Chapter 5 - S-Registers.................................................................................................... 49
5.1 Introduction...................................................................................................................................... 50
5.2 Reading and Assigning S-Register Values ......................................................................................55
5.2.1 Examples of Assigning Values .................................................................................................. 56
5.2.2 Examples of Reading Values .................................................................................................... 56
5.3 AT Command and S-Register Summary ......................................................................................... 56
Chapter 6 - Callback Security and
Remote Configuration...................................................................................................... 57
6.1 Introduction...................................................................................................................................... 58
6.2 Callback Feature Description .......................................................................................................... 58
6.3 Remote Configuration Description................................................................................................... 58
6.3.1 Initial Setup Procedures for Callback and Remote Configuration. ............................................ 58
6.3.2 Remote Configuration Procedures ............................................................................................61
6.4 Remote Configuration and Callback Security AT Commands ......................................................... 62
6.5 Remote Configuration/Callback Security S-Registers ..................................................................... 63
Chapter 7 - DIP-Switch Settings...................................................................................... 65
7.1 Introduction...................................................................................................................................... 66
7.2 DIP-Switch Option Settings ............................................................................................................. 66
7.3 Speaker Volume Control ................................................................................................................. 71
7.4 Recording Option Configurations .................................................................................................... 72
Chapter 8 - Warranty, Service and Tech Support .......................................................... 74
8.1 Introduction...................................................................................................................................... 75
8.2 Multi-Tech Systems, Inc. Warranty & Repairs Policies .................................................................... 75
8.3 Online Warranty Registration .......................................................................................................... 76
8.4 Replacement Parts .......................................................................................................................... 77
8.5 Technical Support ............................................................................................................................ 77
8.6 Internet Sites ................................................................................................................................... 77
Appendixes....................................................................................................................... 78
Appendix A -- Upgrading Your Modem’s Firmware....................................................................................... 79
Appendix B - Troubleshooting ...................................................................................................................... 82
Apendix C - AT Command Summary ........................................................................................................... 87
Appendix D - V.25bis Operation ................................................................................................................... 96
Appendix E - MultiModemBA Cables ........................................................................................................... 102
Appendix F - Regulatory Information............................................................................................................ 103
Index.................................................................................106

Chapter 1 - Introduction and Description

6
MultiModemBA 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 BA series modem, from Multi-Tech
Systems. This User Guide covers various models within the BA series, and unless otherwise noted,
all content should be considered relevant to all models.
Your MultiModem provides data communication at the following rates:
33,600 - 14,400 bps (Enhanced V.34 / V.32bis)
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
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 describes the installation of
PhoneTools, 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 - AT Command Mode Operation
Chapter 4 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 5 - S-Registers
Chapter 5 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.

7
Chapter 1 - Introduction and Description
Chapter 6 - Callback and Remote Configuration
Chapter 6 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 7 - DIP-Switches
Chapter 7 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 8- Warranty, Service & Technical Support
Chapter 8 provides statements on your five-year warranty, instructions for getting modems serviced
at the factory and the procedure for downloading firmware upgrades via FlashROM.
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 - Upgrading Your Modem’s Firmware
Appendix B - Troubleshooting
Appendix C - AT Command Summary
Appendix D - V.25bis Operation
Appendix E - Cabling Diagrams
Appendix F - Regulatory Information
1.3 Modem Features
The MultiModem BA Series modem connections can be made on Public Switched Telephone
Networks ( PSTNs ) and/or point-to-point 2-wire 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.

8
MultiModemBA User Guide
1.3.1 2834 Series Features
Your MT2834BA 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 MT2834BA features ITU V.25bis standard for synchronous dialing, 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.)
1.4 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.

9
Chapter 1 - Introduction and Description
1.5 Technical Specifications
Your data/fax modem meets the specifications listed below:
Tradename MultiModemIITM
Model Numbers MT2834BA, MT2834BAI
Data Rates (modem) 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
Data Rates (fax) 14,400, 9600, 7200, 4800 bps
Data Format 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
Compatibility ITU V.42
bis , V.42, Pending ITU Enhanced V.34 approval, ITU V.34,
AT&T V.32 terbo , ITU V.32 bis , V.32, V.21*, V.22 bis , V.22,
V.23*,V.25 bis , *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)
Error Correction V.42 (LAP-M or MNP 3 & 4) error correction
Data Compression V.42 bis , (4:1 throughput) or MNP 5 (2:1 throughput) data
compression
Speed Conversion Serial port data rates adjustable to 300, 1200, 2400, 4800, 9600,
19,200, 38,400, 57,600 and 115,200 bps
Flow Control Options Xon/Xoff, Hardware RTS/CTS, ENQ/ACK, Unix-to-Unix Copy
Protocol (UUCP) "Spoofing"
Mode of Operation Full duplex over both dial-up lines and 2-wire leased lines; automatic
or manual dialing, automatic or manual answer
Intelligent Features 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 60 characters
Modulation 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

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MultiModemBA User Guide
Fax Modulations 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
Transmit Level -11dBm (dial-up), -9 or -15 dBm (leased-line); dBm level selectable
with DIP-Switch #3 in leased line setting
Frequency Stability ±0.01%
Connectors One DB-25 RS-232C connector; two RJ11 for phone line/telephone
set; power.
Diagnostics Power-on Self Test, Local Analog Loop, Local Digital Loop, Remote
Digital Loop, Back-to-Back Test.
Indicators LEDs for Transmit Data, Receive Data, Carrier Detect, Speed
Indicators, Off Hook, Terminal Ready, Error Correction, Fax, and
Error
Controls Toggle switches for Voice/Data with Originate or Answer, Power On/
Off; and DIP Switches for various modem options.
Speaker Speaker for call progress monitoring
Operating Temperature 0°to 50°C (32°to 120°F)
Power Requirements 115 Volts AC, 60Hz, 0.3amp (2-prong outlet-mounted transformer)
240V/50Hz optional (International).
Dimensions 6.150" x 9.00" x 1.375"
15.6 cm x 22.9 cm x 3.5 cm
Weight 1.6 pounds/0.72 Kg (without transformer)
2.6 pounds/1.18Kg (with transformer)
Limited Warranty Five Years
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.

11
Chapter 1 - Introduction and Description
1.7 Modem LED Indicators
The MultiModem diagnostic LED indicators are shown in Figures 1-1
FXECTROH249614.419.224.028.8CDRDSD
FaxV.42RdyOff Hk2400960014.4K19.2K24.0K28.8KCarrRcvSe d
MT2834BA
Series
I tellige t
Modem Voice/
Data
A sw
Orig
Figure 1-1. MT2834 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.
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. 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.
(24.0) 24,000 bps. 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. This LED is lit when the modem is connected at 19,200 bps.
(14.4) 14,400 bps. (2834 and 1432 models only) 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.32 bis 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.
(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.

12
MultiModemBA User Guide
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 2 - Installation and Connection

14
MultiModemBA User Guide
2.1 What is inYour 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
FXECTROH249614.419.224.028.8CDRDSD
FaxV. 42RdyOff Hk2400960014.4K19.2K24.0K28.8KCarrRcvSe d
MT2834BA
Series
I tellige t
Modem Voice/
Data
A sw
Orig
Figure 2-1. Unpacking
Your package should include:
•MT2834BA data/fax modem
•RJ-11 telephone cord
•AC Power Transformer
•One (1) Quick Start Guide
•One (1) software CD (PhoneToolsTM data communications and fax software)
•This User Guide (on diskette)
If any of these items are missing, contact Tech Support.
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 BA series.

15
Chapter 2 - Installation and Connection
2.2.1 Safety Warnings
1. Use this product only with UL and cUL listed computers.
2. To reduce the risk of fire, use only 26 AWG (.41mm) or larger telephone wiring.
3. Never install telephone wiring during a lightning storm.
4. Never install a telephone jack in wet locations unless the jack is specifically designed for wet
locations.
5. Never touch uninsulated telephone wires or terminals unless the telephone line has been
disconnected at the network interface.
6. Use caution when installing or modifying telephone lines.
7. Avoid using a telephone during an electrical storm. There is a risk of electrical shock from
lightning.
8. Do not use a telephone in the vicinity of a gas leak.
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.
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 7.
DIP-Switch Condition Effect
#5 UP* Selects Answer mode
DOWN Selects Originate mode
#10 UP* Selects Dial-Up operation
DOWN Selects Lease Line operation
* indicates Factory Default setting
2 Verify that the ON/OFF switch at the rear of the modem to the OFF (Down) position.

16
MultiModemBA User Guide
3 Connect the modem to a dial-up line by attaching the RJ-11 telephone cord (provided with your
unit) to the LINE connector on the modem and to a dial-up wall jack. Refer to Figure 2-2.
PHONE LINE
ON
OFF
POWER
EIA RS232C
VOLUME
Figure 2-2. MultiModemBA/BAI Connections
4 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.
5 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 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.
7 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.
2.3 Installing Data Communications Software
Data communications software is designed to send and receive messages. Multi-Tech includes a
data communications software program, PhoneTools, with your modem. However, the modem will
work with any data communications software.
To install PhoneTools, insert the PhoneTools CD in you CD-ROM drive and click the PhoneTools
icon. You will be asked to choose your language. The software will then automatically load onto your
PC.

Chapter 3 - Software Configuration and Modem Basics

18
MultiModemBA User Guide
3.1 Introduction
Chapter 2 described the installation of PhoneTools, a 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 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.
3.2.1 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. 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 AT tention 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.
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

19
Chapter 3 - Software Configuration
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).
3.5 Configuring Software forYour 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.
3.5.1 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.

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MultiModemBA User Guide
3.5.2 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.
3.5.3 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.