Multitech MultiModem MT5600ZDX User manual

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Owners Manual
TM
TM

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Model MT5600ZDX
NOTE: This equipment has been tested and found to comply with the limits for a
Class B 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 residential installation. 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. However, there is no guarantee that interference will not occur
in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning the equipment
off and on, the user is encouraged to try to correct the interference by one or
more of the following measures:
Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different
from that of which the receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.
WARNING: Changes or modifications to this unit not expressly approved by the
party responsible for compliance could void the users authority to operate this
equipment.
The Telephone Consumer Protection Act of 1991 makes it unlawful for any person
to use a computer or other electronic device to send any message via a telephone
fax machine unless such message clearly contains in a margin at the top or bottom
of each page or the first page of the transmission, the date and time it is sent and
an identification of the business or other entity, or other individual sending the
message and the telephone number of the sending machine or such business,
other entity, or individual. See the cover page of your fax software manual for
setup details. This device complies with Part 15 of the FCC rules. Operation is
subject to the following conditions: (1) This device may not cause harmful
interference, and (2) this device must accept any interference received,
including interference that may cause undesired operation.

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Owners Manual
Owners Manual
82068601 Revision B
Model MT5600ZDX
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 © 1997, 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.
Revision Date Description
A 7/14/97 Manual released at Revision A.
B 9/15/98 Added #V, Class 2 fax, and V.90 information.
MultiModemZDX, Multi-Tech, and the Multi-Tech logo are trademarks of Multi-Tech Systems,
Inc. K56flex is a registered trademark of Rockwell and Lucent Technologies Corp.
©Rockwell Semiconductor Systems, Inc. 1997 All Rights Reserved. Reproduced by Permis-
sion. All brand 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]
Fax-Back Service 612-717-5888
Technical Support [phone]
BBS [phone] or [phone]
Internet Address: http://www.multitech.com
Technical Writer: [email protected]

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Model MT5600ZDX
Contents
Chapter 1
Introduction ................................................... 6
Product Description ....................................... 6
What Is in Your Modem Package? ................ 8
Chapter 2
Installation ..................................................... 8
Computer ........................................................ 9
Serial Cable ................................................... 9
Telephone Line ............................................... 9
Safety Warnings ............................................. 9
Communications Software ..........................10
Assemble the Modem ...................................10
Installation Process ..................................... 11
LED Indicators ............................................13
Is Your MultiModemZDX Ready for Use? ..15
Operating Your MultiModemZDX ..............15
Simple Operations .......................................16
Software Configuration ............................... 17
Hardware/Software Confirmation ..............18
Troubleshooting ..........................................18
Chapter 3
AT Commands .............................................. 25
S-Registers ...................................................44
Result Codes ................................................ 56

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Owners Manual
Chapter 4
Local Analog Loopback Test/V.54 Loop 3 .60
Digital Loopback Test/V.54 Loop 2 ............ 61
Digital Loopback Test/V.54 Loop 2 ............ 61
Chapter 5
Introduction .................................................64
Limited Warranty .........................................64
Tech Support ................................................64
Recording Modem Information ..................65
Service ..........................................................65
About the Multi-Tech BBS ..........................66
Logging on to the Multi-Tech BBS .............66
Downloading a File .....................................66
Reading a Message ......................................68
Leaving a Message ......................................68
Bulletins .......................................................68
Using Flash to Upgrade Firmware .............68
About CompuServe/Internet ........................70
About the Multi-Tech Fax-Back Service ....70
Appendix A - Technical Specifications ......................... 71
Appendix B - Regulatory Information .......................... 76
Appendix C - V.90 Information..................................... 82

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Model MT5600ZDX
Introduction
Welcome to the world of data communications. You have acquired one
of the finest intelligent data/fax modems available today, the MultiMo-
demZDX, from Multi-Tech Systems. This Owners Manual will help you
install, configure, test and use your MultiModemZDX.
Product Description
Your MultiModemZDX incorporates new modem technologies called V.90
and K56flexTM, that enable Internet connections at data rates up to 56K bps
over standard telephone lines. This 56K technology is able to propel data
downstream from the Internet to your computer at speeds of up to 56K bps
because data is digitally encoded instead of modulated. Upstream
transmission, mostly keystroke and mouse commands from your computer
to the central site, continue to flow at the conventional data rate of 33.6K
bps.
Your MultiModemZDX offers interactive automatic dialing, as well as
command mode option configuration. You may store four command line/
telephone numbers, of up to 40 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. Themodem
can detect AT&T calling card tones. It is FCC-Registered for connection to
telephone networks without any Data Access Arrangements (DAAs).
Though this modem is capable of 56K bps download performance line impairments, public
telephone infrastructure and other external technological factors currently prevent
maximum 56K bps connections.
The MultiModemZDX is a desktop fax/modem for compatible IBM Personal
Computers; and provides dial-up asynchronous communication capability
with other personal computers, terminals, on-line computer services or
other types of computer systems.
Connection to the phone line and/or an attached telephone device is made
by RJ11 modular type connectors; the PC connection is made via an
RS232C/V.24 serial cable receptacle; and low voltage DC power is supplied
to the MultiModemZDX through a modular power supply connection
included with the modem. All these connections are located on the rear
of the MultiModemZDX. Hardware installation procedures are described in
Chapter 2.

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Owners Manual
General features include:
4Compliance with major ITU-T, TIA, and EIA international standards to
ensure compatibility with other modems.
4Distinguishes data, and fax calls.
4Caller ID to identify your callers phone number (available on U.S.
products).
Data
4Supports V.90 and K56flexTM for data transmission speeds up to 56Kbps,
while maintaining compatibility with lower-speed modems.
Note the V.90 and K56flex standards asymmetrically transfers data--
client downloads at speeds up to 56K bps, client uploads at speeds up
to 33.6K bps.
4Supports the enhanced ITU-T V.34 standard, with data transmission
speeds to 33.6K bps, while also maintaining compatibility with lower-
speed modems.
4Supports V.90 and K56flex speeds plus 33.6K, 31.2K, 28.8K, 26.4K,
24K, 21.6K, 19.2K, 16.8K, 14.4K, 12K, 9.6K, 7.2K, 4.8K, 2.4K, 1.2K,
and 0-300 bps.
4Automatic fallback to slower speeds in noisy line conditions, and fall-
forward to faster speeds as conditions improve (line quality monitoring).
4ITU V.42 LAP-M and MNP Class 3 and 4 error correction.
4ITU V.42bis (4-to-1) and MNP 5 (2-to-1) data compression.
4MNP10 and MNP10ECTM Enhanced Cellular Performance (error correc-
tion).
4H.324 compliant (videophone ready).
4Automatic disabling of compression when transferring already-com-
pressed files.
4Autodial, redial, pulse (rotary) and touch-tone dial.
4Dial tone and busy signal detection for reliable call-progress detection.
4Distinctive ring support to route voice, data, or fax calls on a single
phone line.
4Plug and Play (PnP) serial support.
4FlashROM upgradable.
4Compatibility with the standard AT command set used by most commu-
nication programs.

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Model MT5600ZDX
Fax
4Supports V.17, Class 1and Class 2 Group 3 fax communication
standards, allowing it to communicate with other fax modems as well
as with fax machines.
4Sends and receives faxes from your computer at 14,400 bps, 9600 bps,
7200 bps, 4800 bps, 2400 bps, or 300 bps.
What Is in Your Modem Package?
Your MultiModemZDX has several components. Make sure you have
them all before installing your modem. Your package should include:
MultiModemZDX data/fax modem
DC power supply
One set of four plastic feet
Two sets of Velcro fasteners
Telephone cord
MultiModemZDX Owners Manual
Data Communications Software
One Set-Up diskette
Brochure with warranty registration card
If any of these items are missing, please contact Multi-Tech Systems or your
dealer/distributor.
Installation
In addition to the contents of the MultiModemZDX package, you will
need the following equipment.
Computer
The MultiModemZDX can be connected to any computer with an RS-232
serial port.

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Owners Manual
Serial Cable
You must provide a serial cable to connect the MultiModemZDX to your
computer. Serial cables are available at computer stores and many office
supply stores. The cable must have a DB-25P connector at the modem end.
For IBM and compatible computers, the other end may have a DB-25P
connector or a DB-9S connector, depending on your particular computer
and whether you are using the COM1 or the COM2 serial port. The FCC
requires cables to be shielded.
DB-25 DB-9
Telephone Line
You must have a telephone line with a conveniently located connector
(jack) to accept the cable that comes with the MultiModemZDX. If you
do not have a telephone jack near your computer, you should install an
extension before proceeding.
In North America, telephone extension kits and accessories are available
at electronics stores and wherever telephones are sold. You may also hire
an independent contractor or your local telephone company to do the
work. If you want to add a line for your MultiModemZDX fax modem,
you must contact your telephone company.

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Model MT5600ZDX
Safety Warnings
1. Never install telephone wiring during a lightning storm.
2. 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. Use caution when installing or modifying telephone lines.
5. 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. Do not use the telephone to report a gas leak in the vicinity of the leak.
Communications Software
To operate the ZDX, you must have data and fax communications software.
Data comm software simplifies control of the modem by guiding you through
the process of selecting your serial port, your port speed, and other variables,
and then storing your settings, including frequently called phone numbers,
so they can be recalled with the stroke of a key or the click of a mouse. The
software must be set up, or configured, before you can use it. You must have
Microsoft Windows 3.1 or later to run most prevalent software packages. If
you require software for DOS or for the Macintosh operating systems, please
contact Multi-Tech Sales.
Assemble the Modem
The only assembly required is to mount the feet on the bottom of the modem.
Simply peel the four self-adhesive plastic feet off the backing strip and press
them into the recesses on the bottom of the modem. Alternately, or
additionally, you can use the self-adhesive Velcro patches to mount the
modem to a vertical surface or to keep it from being dislodged on a horizontal
surface.
If you use the Velcro patches, we recommend that you mount them where
they will not obscure the labels on the bottom of the modem. The ZDX has
no special placement restrictions, but we recommend that you place it where
you can see the indicators on the front panel.

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Owners Manual
Installation Process
The installation of the MultiModemZDX 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.
RS232 PHONE LINE
RJ11/Phone Connection
RJ11/PSTN Connection
Power Connector
(to Transformer)
DB25 to Computer
POWER
Figure 2-2. MultiModemZDX Connections
To install your MultiModemZDX:
1. Attach MultiModemZDX to dial-up phone lines using the RJ11 telephone
cord. This is accomplished by plugging one end of the cable provided
with the MultiModemZDX into the telephone jack in your home or office;
and plugging the other end into the LINE jack on the MultiModemZDX.
NOTE
The LINE jack is not interchangeable with the PHONE jack on the
MultiModemZDX. Do not plug the telephone into the LINE jack or the line
cable into the PHONE jack. BABT regulations require that the
telecommunication cable be connected to the modem prior to being
connected to the network.
2. Attach your MultiModemZDX to your PC or terminal with an RS232 (or
V.24) cable (see Figure 2-1 and Figure 2-2). Be sure to tighten the
mounting screws on the DB connectors.
3. Connect your telephone set to phone jack via RJ11 cable.
4. Attach your MultiModemZDX to the AC Power transformer and plugging
the AC connector into a live AC outlet.
NOTE
Use only the power supply provided with the MultiModemZDX. Use of
any other power supply will void the warranty and could damage the
modem.

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Model MT5600ZDX
5. Turn on power by flipping the "ON/OFF" switch on the side of the
MultiModemZDX to the "ON" position.
6. Make sure modem and computer/terminal serial port baud rates are
adjusted. (Note that several programs can check this for you. If you have
MS-DOS 5.0 or higher, a program called MSD.EXE [Microsoft Diagnostics]
is in your DOS directory. Typing MSD at the DOS prompt brings up a
screen that provides a variety of information about your computer. Select
COM ports and it lists information about your com port, e.g., UART Type,
Address, and IRQ, to name a few. Once you know your serial port's UART
type, you can set your communications's software appropriately.)
7. Proceed to Chapter 3 of this manual, or to your data communications
software manual.
✳#
Figure 2-2a. MultiModemZDX Connections
LED Indicators
The MultiModemZDX has ten LED indicators to report MultiModemZDX
status (such as verifying proper installation) and line activity (such as
monitoring the status of a connection).

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Owners Manual
Figure 2-3. MultiModemZDX Front Panel
TD
Transmit Data. The TD LED flashes when data is being
transmitted (on for a space, off for a mark). Signals on this circuit
are generated by the terminal and transferred to the transmitter of
the MultiModemZDX. 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
(TD) LED indicates the status of this circuit.
RD
Receive Data. The RD LED flashes when data is being
received (on for a space, off for a mark). Data signals received
from the remote MultiModemZDX are presented on this line. The
RECEIVE (RD) LED indicates the status of this signal.
CD
Carrier Detect. This LED lights when a valid carrier signal from
another modem is detected.
56
V.90 or K56flex. This LED is lit when connected to an ISP-type K56flex
server. The actual connection speed is contingent upon server
capabilities and line conditions.

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Model MT5600ZDX
28
V.34. This LED is lit when the modem is connected in V.34 mode.
14
V.32bis. This LED is lit when the modem is connected in V.32bis mode.
Note at speeds lower than a V.32bis connection, the
MultiModemZDX speed LEDs remain unlit.
OH
Off Hook. The condition of Off Hook indicates to the central
office that the MultiModemZDX wants the phone line to do some-
thing (i.e., dial or answer a call). This LED is also lit when the
MultiModemZDX has achieved on-line status.
TR
Terminal Ready. When TR is lit, the MultiModemZDX can
answer an incoming call. This signal (TR or DTR) provides a means
for the terminal or computer to control the MultiModemZDX's
connection to the communications channel. A high DTR signal is
required by the MultiModemZDX to be able to communicate. The
state of the TR LED matches that of the DTR circuit on pin 20 of the
RS232/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.

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Owners Manual
Is Your MultiModemZDX Ready for Use?
As soon as you have connected power to the modem, if youre 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 the AT&V<cr> command.
This command lists how your modem is currently configured, the stored
(user) profiles, and the first four stored telephone numbers. If you come
across a setting youre unsure of, refer to Chapter 3 of this manual for AT
command and S-Register explanations and defaults.
If youre a novice, please continue to the next sections of this chapter.
Operating Your MultiModemZDX
You control your MultiModemZDX by issuing AT commands and setting
S-Registers. Right now your MultiModemZDX 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 current default configuration. (If however,
you know that your application does not follow this profile, please refer to
Chapter 3 for AT Commands and S-Registers.)
In operating your MultiModemZDX it is 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 reconfigure
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 lower-case
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

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Model MT5600ZDX
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.
Simple Operations
You can dial 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; a scrambling noise is heard as the modem
negotiates the kind of connection it can make, and once the modems have
settled on a common connection, a connect message on your computers
video is displayed. To hang up a call, enter ATH0<CR>. Your modem will
return on hook, just as if you had returned a phones handset to its cradle.
Your video now displays OK, signifying that your modem is ready for your
next command.
Software Configuration
Communications software must be configured to work with the
MultiModemZDX, your computer, and the remote system it is calling.
Fortunately, most communications programs make the process easy by
providing a default initialization string to your modem as well as defaults for
most of the other required parameters.
Some software programs allow you to select your modem type from a menu.
By this method, initialization strings that correspond to a particular modem
type can be selected to operate optimally with the software in use.
*: Refer to your respective software manual for further information on your
communications software.

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Owners Manual
Figure 2-5. MultiModemZDX Initialization Setup
Other software programs require you enter an initialization string in the
software modem setup screen. If this is the requirement in your software
application, enter the following command string to initialize your modem:
AT&F<cr>. This setting configures your modem to operate optimally with
the software it is utilizing.
Hardware/Software Confirmation
To confirm that your modem (hardware) and communications package
(software) is working properly:
1. Go into terminal mode in your communications package.
2. To determine if your computer and modem are communicating properly,
Enter: AT<CR> At this point your video monitor should display OK. If
the characters you typed do not appear or if double characters appear, see
the troubleshooting section of this chapter.
3. To confirm how your MultiModemZDX is configured, enter AT&V<cr>.
The current MultiModemZDX configuration is displayed as show below.
Example:
AT&V
ACTIVE PROFILE:
B0 E1 L1 M1 N1 QO T V1 W0 X4 Y0 &C0 &D0 &G2 &J0 &K3 &Q5 &R1 &S0 &T4 &X0
&Y0
S00:002 S01:000 S02:043 S03:013 S04:010 S05:008 S06:002 S07:030 S08:002
S09:006
S10:014 S11:255 S12:050 S18:000 S25:005 S26:001 S36:007 S37:000 S38:020
S46:138
S48:007 S95:000

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Model MT5600ZDX
Troubleshooting
Your MultiModemZDX 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:
 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 online;
 The modem cannot connect when answering;
 Slow file transfer;
 Losing data;or
 Garbage characters on the monitor
None of the LEDs Light When the Modem Is On
When you turn on the MultiModemZDX, 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.
4Make sure the modems power switch is on, especially if you normally turn on the
modem by turning on a power strip.
4If the power supply is plugged into a power strip, make sure the power strip is
plugged in, and its power switch is on.
4Make sure the power supply module is firmly connected to the modem and to the
wall outlet or power strip.
4If the power strip is on and the modem switch is on, try moving the modem power
supply to another outlet on the power strip.
4Test the outlet is live by plugging a lamp into it.
4The 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.
*: 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
4Make sure the modem is plugged in and turned on. (See None of the LEDs Light
When the Modem Is On.)

19
Owners Manual
4Make sure you are issuing the modem commands from the data communications
software, either manually in terminal mode or automatically once you have
configured the software. (You cannot send commands to the modem from the DOS
prompt.)
4Make 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 phonebook entry or session settings. Be sure your
modem is not in data mode when you type a command. Use the escape character
sequence to switch to terminal mode. The default escape sequence must wait
at least one second, enter +++, and pause another second or more before
entering a command.
4The E0 and Q1 commands may be in effect, disabling echo and responses. Verify
this with the &V command. To enable echo and responses, enter ATE1Q0<cr>.
4Try 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.
4If 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 automat-
ically. Some connect when the software loads and remain connected until the
program terminates. Others can disconnect without exiting the program. Many
communications software packages also allow multiple terminals to be open, but
only one can access the modem at a time. If your package 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.
4Your 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.
4If 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.
4Is 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.
4Peripheral expansion cards, such as bus mouse and sound cards, may include a
serial port preconfigured 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

20
Model MT5600ZDX
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.
4The 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.
4The 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 5).
The Modem Dials But Cannot Make a Connection
There can be several reasons the MultiModemZDX fails to make a connection.
Possibilities include
 modem is not configured properly.
 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.
4Both local and remote modems may be misconfigured, thus encumbering the
negotiation process between modems. The solution may be to modify modem
parameters via AT command strings. There are other configurations you can