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14.4Kbps MODEM


Using the 14.4Kbps Modem Documentation File.

This file provides installation and operating instructions for the
14.4Kbps MODEM, including internal and external versions. The
information assumes the user has basic computer skills but will
attempt to explain modem operations and command structure. All
sections should be read carefully before beginning any installation
procedures. In addition to following the instructions provided
here, you will also need to consult the documentation supplied with
your communications software.



IMPORTANT NOTICE

FCC Requirements

The Federal Communications Commission (FCC) restricts the way you
can use modems. Read the FCC compliance statement found in Appendix
C of this file.

Telephone Company Requirements

Some telephone companies require notification when any electronic
communications equipment is connected to the telephone lines.
Contact the phone company before connecting your modem to the
telephone line and provide them with the following information:

* The telephone number of the line that you are attaching the
modem.

* The modem's FCC registration number and ringer equivalence
number. These numbers are printed on the FCC label which appears on
the main chip in the center of the internal modem board, or on the
underside of the external modem.

You can connect the modem to various types of telephone jacks. The
acceptable phone jack types are RJ-11, RJ-12, RJ-13, RJ-41S, and
RJ-45S. Most homes and businesses use one of these jacks. If your
phone system does not have a modular jack, you can purchase an
adapter to convert your jack into an RJ-11C jack. Adapters may be
purchased from any local phone or electronics store.










***************************************************************

QUICKSTART

If you are familiar with personal computers and modems, you may
follow the accompanying diagram to quickly install either the
INTERNAL or EXTERNAL version of the 14.4Kbps modem in your system.
Make all necessary connections as shown in those diagrams.

To verify line connection, lift your telephone receiver to check
for a dial tone. If you are using a dedicated line, plug the line
into any phone. After hearing the tone, power on your computer,
load your communication software, and put the program into command
mode. If you do not hear a dial tone, see Section Eight:
Troubleshooting.

****************************************************************

Introduction

The 14.4Kbps modem (internal or external version) combines
high-speed data, modem, and fax capability on a single device. It
features V.32bis, which provides high-speed data transmission plus
support for V.42bis (error correction) and MNP5 (data compression).

Features

* Data transmission rates of 14.4K, 12K, 9600, 7200, 4800, 2400,
1200, or 300bps.
* 100% data compatibility with the Hayes 'AT' command set.
* Programmable speaker volume control
* Automatic voice and data switching.
* Auto-speed sensing.
* V.32bis, V.42bis, and MNP5 are supported as well as V.42 and MNP
2-4 error correction, offering throughput speed of 57,600 bps.
* Group III send and receive fax capability with support for Class
1 and Class 2 fax commands.
* Supports 100 x 196 high resolution and 100 x 98 low resolution.
* Supports high-level data-link control framing.
* Communication ports selectable as COM1, 2, 3, or 4 using
interrupts 3, 4, 5, or 7 (INTERNAL ONLY).



To get started, go to:

* SECTION ONE IF YOU HAVE THE INTERNAL MODEL.

* SECTION TWO IF YOU HAVE THE EXTERNAL MODEL.





NOTE ON TERMINOLOGY: When you encounter the following acronyms,
keep in mind their meanings:

DTE. Data Terminal Equipment. The computer or terminal, either
local (yours), or the remote (the one you're communicating with).
(computer-to-modem link)

DCE. Data Communications Equipment. The local and/or remote modem.
(modem-to-modem link)

DTR. Data Terminal Ready. Computer provides this signal to the
attached modem indicating that it is ready to receive data.


Suggested Additional Technical Resource:

* The Complete Modem Reference, Gilbert Held, John Wiley & Sons,
Inc.


Installation Hints

Your MODEM has been initialized during factory final test for
optimum performance with included fax communications software. The
following initialization (INIT) string has been found to work with
many popular communication packages:

AT&F~~~E1V1X4&C1&D2%E1

Some bulletin boards and information services have problems with
data compression. If so, add %C0 (0=zero) to the init string.

If you experience difficulties sending or receiving faxes, please
disable all TSR (terminate and stay resident) programs. A TSR
program is a program which remains in memory after it loads. The
easiest way to test the fax send/receive function by disabling the
TSRs is to boot your computer with a plain DOS boot diskette (no
config.sys or autoexec.bat files on the boot diskette). Change to
the directory containing your fax software. Load the software and
send a fax.

If you experience a data connection difficulty with a U.S. Robotics
HST Dual Standard Modem on a BBS, the following should allow you to
connect. First, set the modem software to a DTE speed of 9600. Then
enter:

ATN0 Follows the S37 Register
ATS37=9 Forces modem to connect at 9600 bps.






HOW THIS FILE IS ORGANIZED

Quick Start. If you are familiar with modem operations, this
abbreviated procedure provides a short cut for installing either an
internal or external version of the 14.4Kbps modem. Otherwise, read
Section One before continuing.

Section One and Two : Getting Started. These sections provide
communication settings (internal only), physical installation
instructions (including how to connect the phone line), and
procedures for testing the connection). Refer to your
Communications Software Manual for fax command operation.

Section Three: Data Modem Operation. A discussion of data modem
functions and AT commands and syntax. Also included are definitions
of the modem's S-Registers. These registers are used to change
certain operating characteristics and obtain information about the
modem's state of readiness, as well as test operation.

Section Four: MNP Operation. This section explains how to make use
of the Microcom Networking Protocols. MNP is an error correction
protocol developed by Microcom and is widely supported by modem
manufacturers.

Section Five: Error Correction: V.42/V.42bis. V.42 and V.42bis are
CCITT (Consultative Committee on International Telegraph and
Telephone) standards for error correction and data compression,
respectively. This section describes the AT commands and
S-registers which activate and control these functions.

Section Six: V.32bis/V.32 Operation: A brief discussion of these
CCITT standards for high-speed data transmission.

Section Seven: Diagnostics. Tests may be used to evaluate the
modem's state of operation, its connection, and the communications
link between the 14.4K Modem and the remote modem.

Section Eight: Troubleshooting. This provides a description of the
most common problems which may be encountered during installation
and operation along with possible solutions.

Appendices. These include technical specifications and FCC
compliance information as well as a comprehensive glossary.











Contents

Introduction

Section One: Getting Started (Internal)
1.1 14.4Kbps modem Package
1.2 Communication Settings
1.3 Installing the 14.4Kbps modem
1.4 Connecting the Phone Line
1.4.1 Connecting the Line to the 14.4Kbps Modem
1.4.2 Testing the Connection

Section Two: Getting Started (External)
2.1 14.4Kbps modem Package
2.2 Operational Requirements
2.3 Connecting the Phone Line
2.4 Preparing the System
2.5 Testing the Modem
2.6 Testing the Connection

Section Three: Data Modem Operation
3.1 Making a Call
3.2 Touch-Tone and Pulse Dialing
3.3 Pause While Dialing
3.4 Using the Hook Flash
3.5 Wait for a Subsequent Dial Tone
3.6 Wait for Silence
3.7 Resume Command State after Dialing
3.8 Switch Hook Control
3.9 Manual Dialing
3.10 Manual Answer
3.11 Controlling the Speaker
3.12 Dial Stored Number
3.13 The AT Command Set
3.13.1 Basic Command Set
3.13.2 Extended Command Set
3.14 S-Registers

Section Four: MNP Operation
4.1 Introduction
4.2 MNP Data Mode
4.3 AT Commands for MNP Operation
4.4 S-Register Values for MNP Operation

Section Five: Error Correction (V.42bis)
5.1 Introduction
5.2 S-Register Values for Error Correction
5.2.1 Negotiation Fallback
5.2.2 Delay Before Forced Connect
5.2.3 Protocol Selection
5.2.4 Negotiation Action
5.2.5 Bit-Mapped Registers

5.2.7 Connect Failure Cause
5.2.8 Extended Results Code
5.3 AT Commands for Error Correction

Section Six:V.32bis/V.32 Operation

Section Seven: Diagnostics
7.1 Local Analog Loopback Test
7.2 Local Analog Loopback With Self-Test
7.3 Remote Digital Loopback Test
7.4 Remote Digital Loopback With Self Test

Section Eight: Troubleshooting

Appendix A: How to Set Bit-Mapped Registers
Appendix B: Technical Specifications
Appendix C: Compliance Information
Glossary







































Section One: Getting Started: Internal Model

This section explains how to install the 14.4Kbps internal Modem
into your computer.

1.1 14.4Kbps Modem Package

Verify that your modem package contains the following items:

* 14.4Kbps modem Board
* RJ-11 Telephone Cable
* Communication Software and manual
* Software diskette containing this file, and sheet with diagrams.

1.2 Communication Settings

The 14.4Kbps Modem can be configured as COM1, COM2, COM3, or COM4.
The default setting for the modem is COM1 utilizing IRQ4. The
following shows standard COM port and IRQ settings:

COM1/IRQ4 COM2/IRQ3 COM3/IRQ4 COM4/IRQ3

Because two COM ports will share a single interrupt, you must be
careful in choosing which device will share the same interrupt with
the modem. Generally, the modem cannot share the same interrupt
with any device that is driven by a TSR (terminate and stay
resident) program. For example, if you have a mouse on COM1, the
modem cannot be set to COM3; if the mouse is on COM2, the modem
cannot be set to COM4.

One way to avoid interrupt sharing is to select a non-standard
interrupt (i.e., IRQ) if it is available, such as IRQ5. However,
your communications software must be able to select this
non-standard interrupt as well.

1. Remove the 14.4Kbps Modem from its anti-static bag handling it
by its edges and metal retaining bracket. Be careful not to touch
the edge connector or any of the components on the modem.

2. Determine how many serial ports are already installed in your
system. Set the jumpers on the 14.4Kbps Modem for the next
available port. See the accompanying illustration for assistance in
jumper settings.


1.3 Installing the 14.4Kbps modem

This section provides step by step instructions for installing your
14.4Kbps Internal Modem.

1. Power off the computer and disconnect any attached devices and
power cords.

2. Remove the computer's cover and locate an available 8- or 16-bit
expansion slot. Remove that expansion slot cover and save the
screw.

3. Carefully insert the 14.4Kbps modem into the expansion slot
applying pressure to the upper metal edge until it snaps into
place.

4. Secure the 14.4Kbps modem card into place by aligning the
14.4Kbps modem's metal retaining bracket with the hole in the top
edge of the system's unit rear panel. Fasten the metal bracket with
the screw removed earlier from the expansion slot cover.

5. Replace the computer cover.


1.4 Connecting the Phone Line

An RJ-11 cable is provided with the purchase of your 14.4Kbps
modem. This section contains information you will need before you
connect the telephone line to the 14.4Kbps modem and explains how
to make the proper connections from the 14.4Kbps modem to your
telephone line.

Before you connect the telephone line to the 14.4Kbps modem, you
should familiarize yourself, if you haven't done so already, with
the information provided at the beginning of this file concerning
FCC and telephone company requirements.


1.4.1 Connecting the Phone Line to the 14.4K Modem
1. Make sure that your computer is still powered down. Plug either
end of the RJ-11 cable provided with the 14.4Kbps modem into the
"LINE" jack on the modem board.

2. If a phone is connected to the telephone wall jack, unplug the
phone cable. Then plug the other end of the 14.4Kbps modem cable
into the telephone wall jack.

3. To continue using the phone, connect the phone cable into the
"PHONE" jack on the 14.4Kbps modem. See Quick Start! illustration
on page 2.


1.4.2 Testing the Connection
1. Check for a dial tone. If a dial tone is heard, proceed with the
next step. If you do not hear a dial tone, check the connections
you made in the previous subsection (1.4.1)

2. Power on the computer.

3. Load your communications software and put the program into
command mode.

4. Type in the command ATZ followed by ENTER and the 14.4Kbps modem
will respond with OK after about three seconds. If the 14.4Kbps
modem does not respond with OK, refer to the Troubleshooting
section of this file.

5. Type ATH1 followed by ENTER and you should hear a dial tone from
the speaker on the modem. To adjust speaker volume, see the section
on AT Commands.

6. Type ATH followed by ENTER to put the modem on hook. This
confirms that the 14.4Kbps modem has been successfully installed
into the computer.

7. Your 14.4Kbps internal Modem is now ready for use. Proceed to
Section Three for Data Modem Operation.


Section Two: Getting Started: External Model

This section explains how to connect the 14.4Kbps external Modem to
your computer.

2.1 14.4Kbps modem Package

Verify that your modem package contains the following items:

* 14.4Kbps modem
* RJ-11 Telephone Cable
* 25-pin to 9-pin RS-232 cable
* 9-pin to 25-pin converter
* AC adapter with cord
* Communication Software and Manual
* Software diskette containing this file, and sheet with diagrams.

2.2 Operational Requirements

The 14.4Kbps Modem has few requirements and is easy to use. Be sure
to read the information on page 1 about connecting to the phone
company. In addition, note the following:

* The communication settings are controlled by the RS-232
interface present in your system. The external modem is connected
to that interface.

* Operating the 14.4Kbps modem with a computer requires
communication software, either as a stand-alone product as included
here, or as part of an application program.

* The 14.4Kbps modem takes a DB-25P (25-pin male connector), but
computer equipment varies. Check the serial ports at the rear of
your machine.

* The serial port requires a socket (female connector) or plug
(male connector) with either 25 or 9 pins. For example, the IBM PC,
XT, and some compatibles require a DB-25S socket connector, while
the IBM AT and some compatibles require a DB-9S socket connector.


2.3 Connecting the Phone Line

An RJ-11 cable is provided with the purchase of your 14.4Kbps
modem. This section contains information you will need before you
connect the telephones line to the 14.4Kbps modem and explains how
to make the proper connections from the 14.4Kbps modem to your
telephone line.

Before you connect the telephone line to the 14.4Kbps modem, you
should familiarize yourself, if you haven't done so already, with
the information provided at the beginning of this file concerning
FCC and telephone company requirements.


2.4 Preparing the Modem

Follow these simple steps to connect the modem to your computer:

1. Turn off your computer and all peripheral devices.

2. Examine the back of the modem and review the attached interfaces
as shown on the accompanying illustration.

3. Check to make sure that power switch is OFF. Then plug the small
end of the power adapter into the power jack on the back of the
modem, and plug the power adapter into a standard 115V AC wall
socket.

Disconnect your present phone cord from the wall jack. Plug the end
of the phone cord that came with the modem into the wall jack, and
the other end into the phone jack at the rear of the modem marked
LINE.

If you want to keep your telephone connected for conventional
calls, plug its cord into the other jack at the rear of the modem
labeled PHONE.

4. Lastly, connect the modem to the computer's serial port with the
RS-232 cable. Attach the appropriate connectors to the modem and to
the serial port. The modem is now ready to be tested and operated.


2.5 Testing the Modem

To verify that your modem is working properly, follow these steps:

Turn on your computer and clear the screen. Then turn the modem's
power switch ON. The following status indicators will flash
accordingly as explained on below:


Indicator Definition Status


TM Test Mode FLASHES when modem is in
test mode and if any errors are
detected.

AA Auto Answer/ ON when in Auto Answer Mode
Answer Mode and when online with the host
modem.

HS High speed ON when the 14.4Kbps modem is
powered on or communicating with
another modem at 4800 bps or
faster.

OH Off Hook ON when the 14.4Kbps modem takes
control of the telephone line
to establish a data link.

SD Send Data FLASHES when a data bit is sent to
the 14.4Kbps modem by the computer.

RD Received Data FLASHES when a data bit is
received from the phone line, or when
the modem sends result codes to the
computer.

TR Terminal ON when the modem receives a
Ready Data Terminal Ready signal from
the computer via the RS-232
cable.

CD Carrier Detect ON when the 14.4Kbps modem
receives a valid data signal
(carrier) from a remote modem. Ready
for data transmission.


2.6 Testing the Connection

1. Turn on the modem (PWR toggle switch) and check for a dial tone.
If a dial tone is heard, continue with the next step. If you do not
hear a dial tone, check the connections you made in 2.4 Preparing
the Modem. Also, refer to Section Eight: Troubleshooting.

2. Power on the computer.

3. Load your communications software and put the program into
command mode.

4. Type in the command ATZ followed by ENTER and the 14.4Kbps modem
will respond with OK. If the 14.4Kbps modem does not respond with
OK, refer to the Troubleshooting section of this file.

5. Type ATH1 followed by ENTER and you should hear a dial tone from
the speaker on the modem. To adjust speaker volume, see the section
on AT Commands.

6. Type ATH followed by ENTER to put the modem on hook. This
confirms that the 14.4Kbps modem has been successfully installed
into the computer.

7. Your 14.4Kbps external Modem is now ready for use. Proceed to
Section Three for Data Modem Operation.














































Section Three: Data Modem Operation

Introduction
The purpose of this section is to define the most commonly used
Hayes-compatible AT commands for use with your modem. In addition,
we've also provided information on extended AT command sets,
S-Registers. Subsequent sections discuss commands and registers for
high-level protocols such as MNP, V.42/V.42bis, and V.32/V.32bis.

Hayes-compatible commands consist of a basic command set and an
extended command set. The basic set involves functions such as
dialing a number, or putting the modem off- or on-hook (i.e.,
lifting or replacing the telephone handset).

Extended commands allow more sophisticated control of the modem
such as transmission speed, or initiating high-level functions like
data compression or error correction. These functions are defined
and controlled by the available protocols mentioned above. A
protocol is a set of standards by which data communications
operate. Every AT command includes an AT prefix, followed
immediately by the command and, in many cases, additional
parameters. Multiple commands can be entered at the same time from
the DOS prompt.

AT Command[parameter]AT Command[parameter] ... PRESS ENTER

Example: ATH or ATH0 tells the modem to disconnect
ATH1 tells the modem to connect, or go off-hook.

Extended commands were developed to provide greater functionality
and control over modem operations. Their format is the same as the
basic command except that an additional parameter is required
following the AT prefix and before the numerical parameter.

This additional parameter comes in three different forms:

the ampersand (&) character: extended AT command

the backslash (\) character: extended AT command for MNP
operation

the percent (%) character: extended AT command for
V.42/V.42bis

Examples: AT&V tells the modem to display (view) its current
configuration and user profile (providing the modem has
non-volatile RAM, meaning it can store limited amounts of
information when power is off.

AT\J1 tells the computer to adjust its speed to match line speed
when a connection is established.

AT%E1 tells the modem to monitor line quality and request a
retrain (adjustment) to the connection.

S-Registers

Modem command language also employs a set of indicators or
registers, which are various numerical values all with a standard
S prefix, hence S-Registers. To a large extent, the values defined
in the S-Registers regulate the operation of the modem and the
function of some commands in the AT command set.

Example: S-Register 6, or S6=n, defines the length of time the
modem will wait for a dial tone. In this case the acceptable range
is 2-255 (in seconds) with a default value of 2. With S6=2, the
modem will wait two seconds for a dial tone when going off-hook
before dialing the first digit of its telephone number.

Data Communication Protocols

This can be more than a little confusing. These protocols represent
various domestic and international standards which enhance modem
performance and reliability. The protocols are activated and
controlled by a variety of extended AT commands and S-Registers.

MNP stands for Microcom Networking Protocol and is a protocol
developed by Microcom for full-duplex, error-free communications.
This protocol detects and corrects errors which can result from
telephone line noise and other signal distortions. There are
several classes of MNP operation also referred to as service
classes. Class 5 maximizes data transfer rate and provides
compression which can significantly increase data throughput.

The V-Dot standards are more numerous, but have a single origin:
the Consulting Committee for International and Telephone and
Telegraph (or CCITT). Some of the lower-level standards such as
V.21 and V.22 have domestic equivalents as developed by the former
Bell System, also referred to as Bell standards. The V.Dot
standards may be summarized as follows:

V.21 The CCITT standard for 300bps communications. Domestic modems
follow the Bell 103 standard, but V.21 can accept international
calls at 300bps.

V.22 The CCITT standard for 1200bps communications. The domestic
equivalent is the Bell 212A standard.

V.22bis The CCITT standard for 2400bps.

V.23 CCITT for 1200bps with a 75bps back channel. This is mostly
used in Europe and South America.

V.32 CCITT standard for 9600bps and 4800bps communications.

V.32bis CCITT standard for an extensive class of high-speed modems
operating at 14,400bps, 12Kbps, 9600bps, 7200bps, and 4800bps.

V.42 CCITT standard for detection and negotiation for LAPM (Link
Access Procedure for Modems) error control. V.42 will also support
MNP levels 2-4.

V.42bis An extension of V.42 specifying the data compression
protocol for use with V.42.


Basic Modem Operation

Use the D command to dial a telephone number with your modem from
the command line, i.e., DOS prompt. The format of the command is
ATD {string}. The string parameter can contain up to 40 characters,
the phone number, and dial modifiers. The dial modifier instructs
the modem how to place the call.

3.1 Making a Call

To dial, issue the command ATD followed by the phone number.

ATD 1234567 [ENTER]

The modem dials the telephone number 1234567 and then waits for a
carrier from a distant, or remote modem. If no carrier is detected
within a given time (default time is 50 seconds), then the modem
automatically releases the line and sends a NO CARRIER result code.
If a carrier is detected, the modem gives a CONNECT result code and
goes on-line, allowing communication with the remote modem. The
connection between the two modems end when any of the following
occurs:

* The local modem loses the carrier signal from the remote modem.

* The Hang Up command (ATH) is sent.

* The DTR interface signal is dropped between the local DTE and
modem with the &D2 or &D3 command in effect.

Any of the above actions will cause the modem to hang up, return to
command mode, and send the NO CARRIER response. Dial modifiers are
summarized as follows:

L Re-dial the last dialed string
P Pulse dialing (default)
T Tone dialing
, Pause before sending the next character
! Hook flash
W Wait for a subsequent dial tone
@ Wait for quiet before proceeding
; Place modem in command state after dialing
^ Disable calling tone.
S=n Dial stored number.



3.2 Touch-Tone and Pulse Dialing

The modem can be used on telephone lines that require either
touch-tone (DTMF) dialing or pulse (rotary) dialing. Pulse dialing
is the default method when you turn on the modem but you can switch
between pulse and tone dialing by using the P or T dial modifiers.
To tell the modem which dialing method to use, type P or T in front
of the numbers to be dialed. Examples:

Touch-Tone Dialing: AT D T 555-1212 [ENTER]
Pulse Dialing: AT D P 555-1212 [ENTER]

Touch-tone and pulse dialing can also be combined in a dial command
line when both dialing methods are required. The following command
line is used to dial through a PBX that uses touch-tone dialing and
the outside lines require pulse dialing:

AT D T 9 W P 555-1212 [ENTER]

This command line tells the modem to touch-tone dial 9 to get an
outside line, wait (W) for a secondary dial tone (see Section Four
on S-Registers), and then pulse dial the number 555-1212.


3.3 Pause While Dialing

The , (comma) dial modifier causes the modem to pause while
dialing. The modem will pause the number of seconds specified in
the Register S8 and then continue dialing. The default value of
Register S8 is two seconds. If a pause time longer than 2 seconds
is necessary, it can be increased by either inserting more than one
, in the dial command line or changing the value of Register S8. An
example of a typical dial command line follows:

AT D 9, 555-1212 [ENTER]

This command accesses the outside (public) telephone line with the
9 parameter. The modem then waits 2 seconds with the , and then
dials the telephone number 555-1212.


3.4 Using the Hook Flash

The ! dial modifier causes the modem to go on-hook (hang up) for
one-half second and is equivalent to holding down the switch-hook
on your telephone for one-half second. This feature is useful when
transferring calls.


3.5 Wait for a Subsequent Dial Tone

The W dial modifier causes the modem to wait for an additional
dial tone before dialing the numbers that follow the W. The length
of time the modem waits is up to the value in Register S7 (default
is 50 seconds). The modem can be instructed to dial through PBXs
(Private Branch Exchanges) or long-distance calling services that
require delays during dialing. This can be done with the W command
to wait for a secondary dial tone or with a , command to pause for
a fixed time and then dial. An example of a Dial command line when
dialing through a PBX follows: AT D 9 W 555-1212 [ENTER].

The 9 accesses the outside (public) telephone line. The W causes
the modem to wait 50 seconds for a secondary dial tone (unless the
default value of Register S7 has been changed). The 555-1212 is the
telephone number to be dialed.


3.6 Wait for Silence

The @ command causes the modem to listen for 5 seconds of silence.
If a 5-second silence has not been detected within the period
specified in the S7 register (default is 50 seconds), the modem
disconnects and returns the NO ANSWER result code. If it detects a
busy signal, it returns a BUSY result code. If the 5 seconds of
silence is detected, then the modem continues dialing the dial
string. Example:

AT DT 9 @ 1 (215) 555-1212 [ENTER]


3.7 Resume Command State after Dialing

The ; (semicolon) dial modifier returns the modem to the command
state after dialing the telephone number. The ; must come at the
end of the command line. It does not connect to the remote
modem, but holds the line for additional commands.

When the modem has finished dialing the number, it returns the OK
message. The semicolon dial modifier is useful when the number to
be entered exceeds 40 characters. The semicolon dial modifier,
breaks the number into two commands. Example:

AT DT 1 123 456; [ENTER]
OK
AT DT 7890 [ENTER]

These two commands dial a single phone number with the ; in the
first command causing the modem to return to command mode without
releasing the line. The second command dials the remaining numbers
and makes the connection to the modem.


3.8 Switch Hook Control

The H command is used to control the telephone line relay. This
command is most commonly used to hang up the phone from command
mode. The format of the command is ATHn where the n parameter
(optional) governs how the line relay is controlled. Either ATH or
ATH0 causes the phone line relay to go on-hook (disconnect). ATH1
causes the phone line relay to go off-hook (connect).


3.9 Manual Dialing

To manually dial the phone, you should be in your communications
software's command mode. Lift the receiver of the telephone and
dial the number you wish to call. Type ATH1 [ENTER] to connect the
modem and then hang up the receiver. Type ATO [ENTER] to tell the
modem to go on-line.


3.10 Manual Answer

When the automatic answer feature (Register S1) is not being used,
incoming calls can be answered manually by typing ATA [ENTER] when
an incoming call is received. The modem will answer the incoming
call and enter on-line mode.


3.11 Controlling the Speaker

The audio speaker is controlled by the M command. It can be
adjusted with the following commands. Default settings are
highlighted:

AT M0 Turns the speaker off

ATM1 Turns the speaker on until carrier is detected (DEFAULT)

AT M2 Leaves the speaker on at all times

AT M3 Turns the speaker on until carrier is detected except
during dialing

The L command is used to adjust the speaker volume. The volume
levels available are:

AT L0, 1 Selects low volume

AT L2 Selects medium volume (DEFAULT)

AT L3 Selects high volume


3.12 Dial Stored Number

This number follows the dial command string, causing the modem to
dial a telephone number previously stored using the command AT&Z.
Up to four entries may be stored and used (0-3).




3.13 The AT Command Set

The 14.4Kbps MODEM supports the standard and extended Hayes AT
command set. These commands are the industry-standard language used
to communicate with the modem. To use these commands, load your
communications software package and enter into command mode.

NOTE: AT commands pertaining to MNP, V.32bis/V.32, and V.42bis/V.42
operation are discussed in their own sections.

The modem is always in one of three modes: the command mode, fax
mode, or data mode. The modem enters command mode when it is turned
on or reset, when it loses a connection with a remote modem, or
when it is in on-line mode and you type certain escape characters.

When the modem is in command mode, it accepts instructions in the
form of commands and return responses. This mode allows the modem
to be configured for a particular application or instructed to
perform a function. These settings will remain active until the
computer has been turned off except for configuration profile
stored in non-volatile RAM. The modem then returns to its default
settings. The modem enters data mode when it has made a connection
with a remote modem and sends the CONNECT response confirming the
connection has been established. Data can then be exchanged.

Every modem command must begin with the characters AT, with the
exception of the A/ command which is described later in this
section. The AT characters are called the attention code. They
signal the modem that one or more modem commands will follow. There
are specific command line guidelines that must be followed:

* Command lines must begin with the AT prefix. Characters must be
in all uppercase or all lowercase.

* Command lines may contain up to 40 characters.

* Space characters in the command line are ignored.

* Command lines must end by pressing the ENTER key

* Line feed character after carriage return is optional and ignored
by the modem.

* Multiple commands may appear on a single line.

* An error in the command line may be corrected by using the
backspace key, with the exception of the AT prefix. Control-H can
be used if the keyboard does not have a backspace key.

Note: Use the command AT&V to display the active configuration and
stored user profiles.



On-Line State
To transmit or receive data, the modem must be in the on-line
state. When placing a call, the modem is put on-line with the dial
command. At the remote end, the modem goes on-line when it is
instructed to answer a call automatically by setting the Register
S0 equal to any number greater than 0 and less than 255. You can
also perform this function with the ATA command.

Escape Sequence
After a connection has been established with a remote modem, you
can return to command mode without breaking that connection by
typing the escape sequence. The escape sequence consists of three
plus characters (+++). It is not necessary to begin this sequence
with the AT attention code, nor do you need to press ENTER after
typing the escape code.

Return to On-Line State
The modem can be returned to the on-line state after the escape
sequence has been issued. To return the modem to the on-line state,
issue the ATO command. To return the modem on-line and then
initiate and equalized retrain sequence, use the command ATO1.

Re-executing the Last Command Line
Each command line sent to the modem remains in the command buffer
until the next AT command is sent or until power to the modem is
turned off. To repeat the last command issued, type in the command
A/. The A/ command is neither preceded by the AT characters nor
followed by ENTER.

Omitting a Parameter
Some commands require a parameter to completely define them. If a
parameter is omitted from a command that requires one, the command
will respond with the default value.

Result Codes
A response is sent by the modem after executing, or trying to
execute a command. The response displays the modems status or the
progress of a call, and can take the form of either words or
digits. The default consists of word responses which are defined
with the V1 command. To receive digit responses rather than word
responses, use the V0 command. To disable the responses entirely,
use the Q1 command. The tables on the next four pages list the
word responses the modem can return, their numeric equivalent, and
a short description of each.











Result Codes


Result Numeric
Code Value Description

OK 0 Modem successfully executed a command line.

CONNECT 1 Connection made at 300 bps.

RING 2 Modem detected an incoming call.

NO CARRIER 3 Modem lost or could not detect a remote
carrier signal within the Register S7 time.

ERROR 4 Modem found an error in the command line.

CONNECT 1200 5 Modem established a connection 1200 at 1200
bps.

NO DIALTONE 6 Modem did not detect a dial tone within 5
seconds after going off-hook.

BUSY 7 Modem detected a busy signal.

NO ANSWER 8 Five seconds of silence was not detected
when using the @ command in the dial command
line.

CONNECT 0600 9 Modem established a connection at 600 bps.

CONNECT 2400 10 Modem established a connection at 2400 bps.

CONNECT 4800 11 Modem established a connection at 4800 bps.

CONNECT 9600 12 Connection made at 9600 bps.

+FCERROR +F4 Fax carrier error.

CONNECT 7200 13 Connected as data modem during an answer.

CONNECT 12000 14 Connection made at 12000 bps.

CONNECT 14400 15 Connection made at 14400 bps.

CONNECT 19200 16 Connection made at 19200 bps.

CONNECT 38400 17 Connection made at 38400 bps.

CONNECT 57600 18 Connection made at 57600 bps.

CONNECT 75TX/ 22
1200RX Modem returns this result code when upon
establishing a V.23 originate connection
when the modem has been instructed to report
the DTE speed to the DTE upon connecting.

CONNECT 23
1200RX/75RX Modem returns this result code when upon
establishing a V.23 answer connection when
the modem has been instructed to report the
DTE speed to the DTE upon connecting.

CARRIER 300 40 Carrier rate of 300 bps.

CARRIER 1200/ 44 V.23 backward channel has been detected.
75

CARRIER 75/ 45 V.23 forward channel has been detected
1200

CARRIER 1200 46 Carrier rate of 1200 bps.

CARRIER 2400 47 Carrier rate of 2400 bps.

CARRIER 4800 48 Carrier rate of 4800 bps.

CARRIER 7200 49 Carrier rate of 7200 bps.

CARRIER 9600 50 Carrier rate of 9600 bps.

CARRIER 12000 51 Carrier rate of 12000 bps.

CARRIER 14400 52 Carrier rate of 14400 bps.

COMPRESSION:
CLASS 5 66 The modem has connected in MNP class 5 and
COMPRESSION message reporting has been
enabled.

COMPRESSION:
V.42bis 67 The modem has connected in V.42bis and
COMPRESSION message reporting has been
enabled.

COMPRESSION:
NONE 69 The modem has connected without data
compression and COMPRESSION message reporting
has been enabled.










3.13.1 Basic Command Set

The following tables list the AT commands and their functions.
Default settings are indicated.

Command Options Description

A none Answer command. The modem will go off-hook,
transmit the answer tone, and wait for a
carrier from the remote modem.

A/ none Re-execute last command. The last command
executed by the modem will execute again. This
command does not require the AT prefix or
ENTER.

AT none Attention characters. The AT command must
appear at the beginning of each command line or
the modem will not execute the command line.

Bn Select communications standard.

n=0 Selects V.22 2100 Hz answer tone at 1200 bps.
(DEFAULT)

n=1 Selects Bell 212A 2225 Hz answer tone at
1200bps.

Cn Turn modem transmit carrier signal on or off.

n=0 Transmit carrier signal off. (DEFAULT)

n=1 Transmit carrier signal on.

D none Dial command. Puts the modem into originate
mode, allowing it to work as an auto-dialer for
connecting to another modem. See Section Two
for additional information.

En Echo back command characters.

n=0 Disables echoing of commands to the screen.

n=1 Enables echoing of commands to the screen.
(DEFAULT)

Fn Select Line Modulation. Selects the line
modulation according to the parameter supplied.

n=0 Auto-detect mode.

n=1 Selects V.21 or Bell 103 according to the AT B
command setting.

n=2 Not supported.

n=3 Selects V.23.

n=4 Selects V.22 or Bell 212A 1200.

n=5 Selects V.22bis 2400.

n=6 Selects V.32bis 4800 or V.32 4800.

n=7 Selects V.32bis 7200.

n=8 Selects V.32bis 9600 or v.32 9600.


n=9 Selects V.32bis 12000.

n=10 Selects V.32bis 14400.

Hn Switch hook control.

n=0 Instructs the modem to go on-hook (hang-up or
disconnect).

n=1 Instructs the modem to go off-hook and enter
command mode.

In Identification. Requests the modem to return
its product identification information.

n=0 Displays the product identification code.

n=1 Displays the ROM checksum.

n=2 Displays ROM checksum as OK or ERROR.

n=3 Displays the firmware revision level.

n=4 Displays OEM-defined identifier string.

n=5 Displays country code number.

n=6 Displays modem data pump model.

Ln Speaker volume.

n=0 Off or low volume.

n=1 Low volume. (DEFAULT)

n=2 Medium volume.

n=3 High volume.

Mn Speaker Control.

n=0 Disables the modem speaker.

n=1 Turns on the modem speaker until carrier has
been detected.(DEFAULT)

n=2 Instructs the modem speaker to stay on at all
time.

n=3 Enables speaker after dialing until connection
is established.

Nn Automode Enable.

n=0 Requires the speed of the connection be that
specified by the value of S37.

n=1 Permits handshaking at any speed supported by
both modems. (DEFAULT)

On Return to on-line state mode.

n=0 Switches the modem from command mode to on-line
mode without dialing.

n=1 Switches from command mode to on-line mode and
initiates an equalizer retrain sequence during
2400 bps operation.

Qn Modem responses enabled or disabled.

n=0 Enables result codes to be issued to the
screen. (DEFAULT)

n=1 Disables result codes to be issued to the
screen.

Sn Change the value of an S-Register. n is the
number of the register whose value is to be
changed (0-95) and n is the new value (0-255).

Sn? Read the value of an S-register. n is the
number of the register whose value is to be
read (0-95).

Vn Result code format.

n=0 Numeric format.

n=1 Verbal format. (DEFAULT).

Wn Error Correction Message Control

n=0 Report DTE speed in error correction mode.
(DEFAULT)

n=1 Report line speed, error correction protocol,
and DTE speed.

n=2 Report DCE speed in error correction mode.


Xn Extended Result Codes. Determines which set of
responses and calling characteristics are used.
X3 allows blind dialing to be enabled by
country parameters. X4 sends all messages.

Response Code n=0 n=1 n=2 n=3 n=4

0 (OK) X X X X X
1 (CONNECT) X X X X X
2 (RING) X X X X X
3 (NO CARRIER) X X X X X
4 (ERROR) X X X X X
8 (NO ANSWER) X X X X X
* (CONNECT XXXX) X X X X X
6 (NO DIAL TONE) O O X X X
7 (BUSY) O O O X X

* Numeric response codes for "CONNECT" are 5, 9-12, 13-18, 22-23,
40, and 44-52. 1 (CONNECT) is a 300bps connection.


Yn Control Long Space Disconnect. Determines
whether or not modem disconnects when it
receives a continuous break from a remote
modem.

n=0 Disabled. (DEFAULT)

n=1 Enabled.

Zn Soft Reset and Restore Profile.

n=0 Restores stored profile 0.

n=1 Restores stored profile 1.

+++ none Escape characters. The escape characters are
known as +++. They will switch from on-line
mode to command mode while preserving the
connection to the remote modem.

This command allows a parameter to be checked
or changed after connecting with a remote
asynchronous modem. Escape characters involve
a timed pause of 1 second (specified in
Register S12), three keystrokes of the + escape
character defined by Register S2) and another
pause (again specified in Register S12).

? S-register contents. Displays the contents of
the last addressed S-register.


3.13.2 Extended Command Set

Commands Options Description

&Cn Data Carrier Detect (DCD) signal.

n=0 Forces DCD signal to be on at all times.
(DEFAULT)

n=1 DCD on indicates presence of data carrier.

&Dn Data Terminal Ready (DTR) signal. Interprets
the ON to OFF transition of the DTR signal from
the DTE according to the & setting as
follows:

n=0 &Q 0, 5, 6. DTR ignored
&Q 1, 4. Modem hangs up; auto-answer not
affected.
&Q 2,3. Modem hangs up; auto-answer inhibited.
(DEFAULT)

n=1 &Q 0, 1 4-6. Asynchronous escape sequence.
&Q 2,3. Modem hangs up; auto-answer inhibited.

n=2 &Q 0-6. Modem hangs up; auto-answer inhibited.

n=3 &Q 0, 1 4-6. Modem does a soft reset as if the
Z command were received; &Y determines which
profile is loaded.
&Q 2,3. Modem hangs up; auto-answer inhibited.

&F Recall factory defaults. Instructs the modem to
use the factory set parameters.

n=0 Recall (restore) factory profile 0.

n=1 Recall (restore) factory profile 1.

&Gn Guard tone select in CCITT mode. Guard tones
are always disabled in the U.S.A.

n=0 Do not use guard tones. (DEFAULT)

n=1 Disables guard tone.

n=2 Selects a guard tone 1800 Hz.

&Jn Telephone Jack Control. Included only for
compatibility and performs no function other
than to load the value of S Register 21
(n= 0 or 1).

&Kn DTE/Modem Flow Control. Determines how the
modem controls the flow of data between the
local DTE and the modem. When the modem
terminal buffer is nearly full, the modem will
either send an XOFF or drop CTS to stop the
data flow; when the buffer is nearly empty, the
modem will either send an XON or raise CTS to
resume the data flow.

n=0 disable flow control

n=3 enable RTS/CTS (DEFAULT for data modem)

n=4 enable XON/XOFF

n=5 enable transparent XON/XOFF

n=6 enable both RTS/CTS and XON/XOFF (DEFAULT for
fax modem)

Note on Flow Control. XON/XOFF is a software-based flow control
method, using standard ASCII control characters to pause or resume
data transmission. RTS/CTS pacing, a hardware-based method, uses an
electrical signal. Signals are exchanged as follows:

RECEIVER TRANSMITTER
CTS ON ------> START SENDING
CTS ON <------ RTS ON (ready to send)
CTS OFF ------>RTS OFF (stop sending)

&Ln Line selection. Informs the modem of the type
of telephone line to which it will be
connected. (NOT SUPPORTED)

n=0 Selects a dialup telephone line. (DEFAULT)

n=1 Selects a leased telephone line. Each modem on
a leased line has its transmitters turned on
continuously, allowing transmission to occur
in both directions at the same time.

&Mn Asynchronous/Synchronous Mode Selection.
Determines the DTR operating mode. The modem
treats the &M command as a subset of the &Q
command.

n=0 Selects direct asynchronous mode. (DEFAULT)

n=1 Selects synchronous connect mode with
asynchronous off-line command mode.

n=2 Same as &M1 except modem will disconnect if DTR
is OFF for more than the period in S25.

n=3 Selects synchronous connect mode with
asynchronous off-line command mode. This mode
allows the DTR to act as a talk/data switch.
The call is initiated while the DTR is
inactive.

&Pn Select Pulse Dial Make/Break ratio. Determines
the ratio between the off-hook (make) and the
on-hook (break) pulse dialing intervals.

n=0 Selects a make/break ratio of 39/61 at 10pps.
Used in the United States and Canada. (DEFAULT)

n=1 Selects a make/break ratio of 33/67 at 10pps.
Used in the United Kingdom and Hong Kong.

n=2 Same as 0 except at 20pps.

n=3 Same as 1 except at 20pps.

&Qn Sync/Async Mode. An extension of the &M command
and is used to control the connection modes
permitted. Used in conjunction with S36 and S48
(see also \N).

n=0 Direct asynchronous mode.

n=1 Synchronous connection with asynchronous off-
line command mode.

n=2 Same as 1 plus enable DTR dialing of directory
zero.

n=3 Same as 1 plus enable DTR to act as talk/data
switch.

n=4 Hayes auto-synchronous mode.

n=5 Modem negotiates an error-corrected link.
(DEFAULT)

n=6 Selects asynchronous operation in normal mode
(i.e., speed buffering).

&Rn RTS/CTS Option. Controls the state of the CTS
signal. CTS is always on in the asynchronous
mode unless AT&K3 has been selected.

n=0 CTS tracks RTS.

n=1 CTS is always active (DEFAULT).

&Sn Data Set Ready (DSR) signal.

n=0 Causes DSR signal to be active at all times.
(DEFAULT)

n=1 Causes DSR signal to be active according to the
V.25 protocol.

&Tn Test and Diagnostics. Refer to the Diagnostics
section for more information.

n=0 Terminates any test in progress.

n=1 Executes the local analog loopback test.

n=3 Executes the local digital loopback test.

n=4 Enables the modem to accept a request from a
remote modem for a digital loopback test.
(DEFAULT)

n=5 Instructs the modem to deny a request from a
remote modem for a digital loopback test.

n=6 Executes the remote digital loopback test.

n=7 Executes the remote digital loopback test with
a self test.

n=8 Executes the local analog loopback test with a
self test.

&V none View current configuration and user profile.
Displays the active configuration and stored
user profiles.

&Wn Store user profile. Saves the current
configuration into non-volatile RAM as one of
two user profiles. Also use this command to
write initialization strings.

n=0 saves as user profile 0.

n=1 saves as user profile 1.

&Xn Select Synchronous Clock Source. Selects the
source of the transmit clock for the
synchronous mode of operation. The parameter
value, if valid, is written to S27 (bits 4 and
5). In asynchronous mode, the transmit and
receive clocks are turned OFF. (EXTERNAL modem
only)

n=0 Selects internal timing.

n=1 Selects external timing.

n=2 Selects slave receive timing. The transmit
clock signal is derived from the incoming
carrier.

&Yn Designate Default User Profile. Specifies which
of two user profiles will be loaded into the
active configuration at power-up.

n=0 Selects user profile 0.

n=1 Selects user profile 1.


&Zn=x none Store Phone Number. Stores a 36-digit dial
string (x) in the specified entry (0-3) for
later dialing. See the ATDS=n command (3.12
Dial Stored Number). An individual entry may be
made up to 40 digits, but the total number of
digits in all entries may not exceed 114.

S=n none Dial Stored Number. Follows the dial command
string, causing the modem to dial a telephone
number previously stored using the AT&Zn
command.


3.14 The S-Registers

This section defines the purpose of the modem registers, explains
how to read and change register values, how to access a register
repeatedly, and sequentially lists the registers and describes
their functions. These registers affect various operating
characteristics and allow you to obtain information about the
modem, as well as test the modem. Each register has a factory-set
value, which you can read or change to fit your needs. To learn how
to set bit-mapped registers and how their values are calculated,
refer to Appendix A.

Reading a Register Value
To read the current value of a register, type: AT Sn? [ENTER],
where n is a register number. The modem will respond with the
decimal value of the register in three digit form. This will be
followed by OK or 0.

To read values from more than one register, type: AT Sn? Sn?
[ENTER] from the command mode.

To read the register values of S0 and S1, type AT S0? S1? [ENTER]

The modem will display the first register value, a carriage return,
the next register value, a carriage return, and OK or 0.


Changing a Register Value
To change a register value, use the Sn command (ATSn=v), where n is
a register number and v is the new value you want to assign to the
register. Type: AT S0=3 [ENTER] to have the modem automatically
answer incoming calls after the third ring. The changed values
remain in effect until the modem is turned off and on or reset.
The modem then returns to its default settings.


Accessing a Register Repeatedly
The modem automatically places a pointer at the last register whose
value was read or changed. The pointer provides a fast way of
displaying or changing register values. Type: AT S0? [ENTER] to
read the value of Register S0. The modem responds with the value of
Register S0 and places a pointer at that register automatically.

Type: AT=0 [ENTER] to change the value in Register S0 to 0.
(Neither the S command nor the register number has to be specified;
the pointer handles this task.)

Type: AT? [ENTER] to read the S0 value. NOTE: The pointer remains
set at the last register accessed until the S command is used to
read or change the value of a different register. The pointer is
then set to the register whose value is displayed or changed.



S-Register Descriptions

The following table lists the modems registers and their functions.

Reg. Range Units Default Definition

S0 0-255 rings 2 Auto-answer

Description: Holds the number of rings the modem will wait before
answering the phone. If this register is set to zero, the modem
will not answer the phone. In terminal mode, make sure this is ON
(S0 equal to anything but zero) with %C1 and %D1 in the active
profile.


S1 0-255 rings 0 Count incoming rings

Description: Counts the number of rings detected on the line. The
register is cleared if a ring is not detected over an eight second
time period. If the register value equal the value contained in S0,
the modem will answer the phone.


S2 0-255 rings 43 Escape character value.

Description: Contains the ASCII value of the character used as the
Escape Code. This enables the modem to switch from on-line mode to
command mode without losing the connection to the remote modem.


S3 0-127 ASCII 13 Carriage return character.

Description: Contains the ASCII value of the character used to send
a carriage return. This character terminates both command lines and
result codes.


S4 0-127 ASCII 10 Line feed character.

Description: Contains the ASCII value of the character used to send
a line feed. The modem sends the line feed character after a
carriage return only when word responses are sent.


S5 0-32 ASCII 8 Backspace character.

Description: Contains the ASCII value of the character used to
backspace. This character is both the character created by pressing
the Backspace key and the character echoed to move the cursor to
the left.




S6 2-255 seconds 2 Wait time for Blind Dialing.

Description: Sets the length of time to pause after the modem goes
off-hook before the modem dials the first digit of the telephone
number.


S7 1-255 seconds 50 Wait for carrier after dial.

Description: Defines two delay times: (1) time that the local modem
waits for the carrier from the remote modem before hanging up; (2)
time that the modem waits when the Wait for Dial Tone call progress
feature (W in dial string) is in effect.


S8 0-255 seconds 2 Pause time for dial delay.

Description: Determines how long the modem should pause when it
sees a comma in the dialing string.


S9 1-255 seconds 6/10 Carrier detect.

Description: Determines the amount of time in tenths of a second
from when the modem recognizes a loss of carrier to when it will
hang up.


S10 1-255 seconds 14 (1.4) Lost Carrier to Hang Up Delay.

Description: Sets the length of time tenths of a second, that the
modem waits before hanging up after the loss of a carrier. This
allows for a temporary carrier loss without causing the local modem
to disconnect. When register S10 is set to 255, the modem functions
as if a carrier is always present. The actual interval the modem
waits before disconnecting is the value in S10 minus the value in
S9. If this value is set smaller than the value contained in
S9, the modem disconnects before it recognizes its carrier.


S11 Reserved.


S12 0-255 seconds 50(1) Escape code guard time*.

Description: Controls the delay time before and after typing escape
sequence codes.

*in one-fiftieth second increments


S13 Reserved.


S14 Bit Mapped AA,hex Bit mapped registers.

Provides the following functions (defaults are highlighted):

BIT Definition and Options

Bit 0 IGNORED

Bit 1 ATE (command echo)

0 Do not echo commands
1 Echo commands (DEFAULT)

Bit 2 ATQ (result code display)

0 Send responses (DEFAULT)
1 Do not send responses

Bit 3 ATV (word or number responses)

0 Send number responses
1 Send word responses (DEFAULT)

Bit 4 RESERVED.

Bit 5 Dial Method (ATP or ATT)

0 Touch-Tone (T) (DEFAULT)
1 Pulse (P)

Bit 6 RESERVED.

Bit 7 Answer/originate operation

0 Answer (A and R)
1 Originate (D) (DEFAULT)


S15 Reserved

S16 Bit Mapped 80,hex Modem test options.

Provides the following functions (defaults are highlighted):

Bit Definition and Options

Bit 0 Local analog loopback test

0 Disabled (&T0) (DEFAULT)
1 Enabled (&T)

Bit 1 NOT USED

Bit 2 Local digital loopback test

0 Disabled (&T0) (DEFAULT)
1 Enabled (&T3)

Bit 3 Remote digital loopback test

0 Disabled (&T0) (DEFAULT)
1 Enabled (&T6)

Bit 4 Initiate remote digital loopback

0 Loopback not in progress (&T0)
(DEFAULT)
1 Loopback in progress (&T7)

Bit 5 Remote digital loopback with error count

0 Disabled (&T0) (DEFAULT)
1 Enabled (&T7)

Bit 6 Local analog loopback with self test

0 Disabled (&T0) (DEFAULT)
1 Enabled (&T8)

Bit 7 NOT USED


S17 Reserved


S18 0-255 seconds 0 Test timer.

Description: Determines how long a diagnostic test will be allowed
to run before being returned to the command mode. The test timer
is disabled with the value set to zero.


S19 Reserved


S20 Reserved


S21 Bit Mapped Bit mapped registers.
00,hex Provides the following
functions:

Bit Definition and Options

Bit 0 Telephone jack type
0 RJ-11, RJ-41S, RJ-45S (&J0)
(DEFAULT)
1 RJ-12, RJ-13 (&J1)

Bit 1 RESERVED

Bit 2 RTS (Request to Send)/CTS(Clear to Send)
(&Rn)
0 CTS tracks RTS (DEFAULT)
1 Modem ignores RTS

Bit 3,4 Data Terminal Ready (DTR)
(&Dn)
0 = &D0 selected (DEFAULT)
1 = &D1 selected
2 = &D2 selected
3 = &D3 selected

Bit 5 Data Carrier Detect (DCD)
0 DCD is always active (&C0) (DEFAULT)
1 DCD is active when remote
carrier is detected (&C1)

Bit 6 Data Set Ready (DSR)
0 DSR is always active (&S0) (DEFAULT)
1 DSR is active when handshaking begins
(&S1)

Bit 7 Long space disconnect
0 Disabled (Y0) (DEFAULT)
1 Enabled (Y1)


S22 Bit Mapped 75,hex Bit mapped registers.

Provides the following functions (asterisk indicates default):

Bit Definition and Options

Bit 0, 1 Speaker volume

0 = OFF (L0)
1 = Low volume (L1) (DEFAULT)
2 = Medium volume (L2)
3 = High volume (L3)

Bit 2, 3 Speaker Control

0 = Speaker turned off (M0)
1 = Speaker on until carrier
detected (M1) (DEFAULT)
2 = Speaker always on (M2)
3 = Speaker on until carrier
detected, off when dialing (M3)

Bit 4, 5, 6 Limit Result Codes

0 = X0
4 = X1
5 = X2
6 = X3
7 = X4 (DEFAULT)

Bit 7 Reserved.


S23 Bit Mapped 07, hex Bit mapped registers.

Provides the following functions. Defaults are highlighted.

Bit Definition and Options

Bit 0 Request from remote modem
for digital loopback test.

0 Ignore request (&T5)
1 Grant request (&T4) (DEFAULT)

Bit 1, 2, 3 Communications Rate
0 0-300 bps
1 600 bps
2 1200 bps
3 2400 bps (DEFAULT)
4 4800 bps
5 9600 bps
6 19200 bps

Bit 4,5 Parity Setting
0 even
1 not used
2 odd
3 none

Bit 6, 7 Guard Tones
0 = none (&G0) (DEFAULT)
1 = none (&G1)
2 = 1800 Hz (&G2)


S24 0-255 seconds 0 Sleep Inactivity Timer.

Description. Sets the length of time that the modem operates in
normal mode with no line activity before entering low power sleep
mode.


S25 0-255 seconds 5 Asynchronous DTR Delay

Description: Determines the time interval that the modem will
ignore a change in the DTR status.


S26 0-255 seconds 1 Delay Interval.

Description: RTS to CTS delay interval (in hundredths of a
second).


S27 Bit Mapped Bit mapped registers.
9, hex

Bit 0, 1, and 3 are reserved.

Bit Definition and Options

Bit 2 Line Type (NOT SUPPORTED)

0 Dialup line (&L0)
1 Leased line (&L1)

Bit 4,5 Clock Source Selection

0 Internal clock (&X0) (DEFAULT)
1 External clock (&X1)
2 Slave clock (&X2)

Bit 6
0 CCITT V.22/V.22bis standard
(B0)(DEFAULT)
1 Bell 212A standard (B1)

Bit 7 Reserved.

S28 Bit Mapped Bit mapped registers

Bit Definition and Options

Bit 0 V.23 split speed (\Wn) (DEFAULT)
0 = Disabled (\W0) (DEFAULT)
1 = Enabled (\W1)

Bit 1 V.23 split speed direction
0 = 75bps transmit (%F0) (DEFAULT)
1 = 1200bps transmit (%F1)

Bit 2 V.23 half-duplex
0 = disabled (DEFAULT)
1 = enabled (%F3)

Bit 3, 4 Pulse dialing (&Pn)
0 = 512 (&P0) (DEFAULT)
1 = 1024 (&P1)
2 = 2048 (&P2)
3 = 4096 (&P3)

Bit 5, 6, 7 Reserved


S29 Reserved.


S30 0-255 seconds 0 Inactivity Timer

Description: Determines the length of time (in tens of a
second) that the modem will wait before disconnecting when no data
is sent or received.


S31 2 Bit Mapped Options

Bit Definition and Options

Bit 0 RESERVED

Bit 1 Controls auto line speed detection.
0 = disabled (N0)
1 = enabled (N1) (DEFAULT)

Bit 2,3 Controls error correction progress
messages (Wn)
0 = DTE speed only (W0) (DEFAULT)
1 = full reporting (W1)
2 = DCE speed only (W2)

Bit 4-7 RESERVED


S32 0-255 ASCII 17 XON Character

Description: Sets the value of the XON character.


S33 0-255 ASCII 19 XOFF Character

Description: Sets the value of the XOFF character.


S34-35 Reserved.


S36 7 Bit Mapped Options

Bit Definition and Options

Bit 0-2 Indicates what happens during a LAPM
failure. These fallback options take
effect immediately upon connection if
S48=128. If an invalid number is entered,
the number is accepted into the register,
but S36 acts as if the default value has
been entered.

0 = modem disconnects
1 = modem stays online; establishes a
direct mode connection.
2 = Reserved.
3 = modem stays online; establishes a
normal mode connection.
4 = attempts MNP connection; if it fails,
modem disconnects.
5 = attempts MNP connection; if it fails,
establishes a direct mode connection.
6 = Reserved.
7 = attempts MNP connection; if it fails,
establishes a normal mode connection.
(DEFAULT)

Bit 3-7 Reserved.


S37 0-12 0 Telephone Line Speed

Description: Desired Line Connection Speed. This is interlinked
with the Fn command. If an invalid number is entered, the number is
accepted into the register, but S37 will act as if the default
value has been entered.

Bit Definition and Options

Bit 0-3 0 = Attempt auto mode connection (F0)
(DEFAULT)
1-3 = Attempt to connect at 300 bps. (F1)
4 = Reserved.
5 = Attempt to connect at 1200 bps. (F4)
6 = Attempt to connect at 2400 bps. (F5)
7 = Attempt to connect at V.23 at 600/1200
bps. (F3)
8 = Attempt to connect at 4800 bps. (F6)
9 = Attempt to connect at 9600 bps. (F8)
10 = Attempt to connect at 12K bps. (F9)
11 = Attempt to connect at 14.4Kbps (F10)
12 = Attempt to connect at 7200 bps. (F7)

Bit 4-7 RESERVED.


S38 0-255 seconds 20 Delay Before Forced Hangup

Description: Specifies the delay between the modems receipt of the
H command to disconnect. Applies to error correction only. This
register can be used to ensure that data in the buffer is sent
before the modem disconnects. If S38=0-254, the modem will wait
that number of seconds before disconnecting. If S38=255, the modem
does not time out and continues to deliver data in the buffer until
the connection is lost or the data is delivered.


S39 Bit Mapped 3 Bit Mapped Registers

Bit Definition and Options

Bit 0-2 Status of Command Options
0 = no flow control
3 = RTS/CTS (&K3) (DEFAULT)
4 = XON/XOFF (&K4)
5 = Transparent XON/XOFF (&K5)
6 = Both methods (&K6)

Bits 3-7 Reserved


S40 Bit Mapped 105 Bit Mapped Registers

Bit 0 MNP Extended Services
0 = disabled (-K0)
1 = enabled (-K1) (DEFAULT)

Bit 1 Power Level Adjustment for Cellular Use ()Mn)
0 = auto adjustment ()M0) (DEFAULT)
1 = force adjustment ()M1)

Bit 2 MNP Link Negotiation Speed (*H1)
0 = highest speed (*H0) (DEFAULT)
1 = 1200 bps (*H1)

Bits 3-5 Break Handling (\Kn)
0 = \K0 1 = \K1
2 = \K2 3 = \K3
4 = \K4 5 = \K5 (DEFAULT)

Bits 6-7 MNP Block Size
0 = 64 chars. (\A0)
1 = 128 chars. (\A1)
2 = 192 chars. (\A2) (DEFAULT)
3 = 256 chars. (\A3)

S41 Bit Mapped 3 Bit Mapped Registers (for MNP)

Bits 0-1 Compression selection (%Cn)
0 = disabled (%C0)
1 = MNP5 (%C1)
2 = V.42bis (%C2)
3 = MNP5 and V.42bis (%C3)(DEFAULT)

Bit 2 Auto retrain
0 = retrains disabled (%E0) (DEFAULT)
1 = retrains enabled (%E1)

Bit 3 Modem to Modem Flow Control
0 = disabled (\G0) (DEFAULT)
1 = enabled (\G1)

Bit 4 Block Mode Control
0 = stream mode (\L0) (DEFAULT)
1 = block mode (\L1)

Bits 5-7 Reserved

S42-45 Reserved

S46 136 or 138 138 Data Compression Control

136 = error correction protocol with no
compression

138 = error correction protocol
with compression (DEFAULT)

S48 0, 7, 128 7 V.42 Negotiation Action

0 = Disable negotiation and proceed with LAPM.
7 = Enable negotiation. (DEFAULT)
128 = Disable negotiation and proceed with fallback action
specified in S36.

S49-81 Reserved

S82 3, 7, 128 128 Break Handling Option

Description: Used to get the attention of the remote modem. Three
types of break signals are provided:

3 = Expedited. Modem sends a break immediately; data integrity
is maintained.
7 = Destructive. Break is sent immediately and data being
processed at time of break is destroyed.
128 = In Sequence. Modem sends a break in sequence; data
integrity is maintained (DEFAULT).

S86 N/A Connection Failure Cause Code

Description: When the modem issues a NO CARRIER result code, a
value is written to the S register to help determine the
cause for the failed connection. The values are as follows:

0 = normal disconnect; no error occurred.
4 = loss of carrier
5 = V.42 negotiation failed to detect an error correction
modem at the other end.
9 = the modems could not find a common protocol.
12 = normal disconnect initiated by remote modem.
13 = remote modem does not respond after 10 re-transmissions
of the same message.
14 = protocol violation.

S91 0 to -15 dBm 10 PSTN Transmit Level

Description: Sets the transmit level, in dBm, for the PSTN mode. In
some countries, this level cannot be changed and there are checks
to prevent transmit level change.


S92 0 to -15 dBm 10 Fax Transmit Level

Description: Sets the transmit level, in dBm, for the fax mode. In
some countries, this level cannot be changed and there are checks
to prevent transmit level change.

S95 SEE SECTION 4.4: S-Registers for MNP Operation














Section Four: MNP Operation

4.1 Introduction

MNP (Microcom Networking Protocol) is a data communications
protocol developed by Microcom for full duplex, error-free
communications over telephone lines. This protocol detects and
corrects errors which can result from telephone line noise and
other signal distortions.

NOTE: MNP can only operate at speeds of 2400bps or higher.

There are several levels of MNP operation available also referred
to as service classes. The service class refers to the following
techniques the modem uses to transfer data. The 14.4Kbps Modem
supports classes 2, 3, 4, and 5 and these classes are summarized as
follows:

CLASS 2. Uses an asynchronous, byte-oriented format in which
standard byte-framing techniques (start and stop bits) and
full-duplex transmission are used.

CLASS 3. Uses a synchronous, bit-oriented format in which standard
byte-framing techniques are removed. This increases throughput by
approximately 20%.

CLASS 4. Optimizes performance by using more efficient framing
techniques and allowing for transmission of large data blocks. Data
block size is adjusted based on the quality of the telephone line
(smaller for poor lines; larger for higher quality lines). This
technique reduces the number of retransmissions and maximizes
transfer rate based on the quality of the phone line.

CLASS 5. Includes all the features of CLASS 4 and also features
data compression. Both downloaded and interactive real-time data
are compressed. A significant increase on most data throughput can
be realized. The AT%C1 command enables this class. If MNP 5 is
disabled, the Modem defaults to Class 4. MNP5 and MNP 4 are not
compatible.


4.2 MNP Data Mode

After establishing the MNP connection, the modem will perform all
functions performed during normal data mode EXCEPT:

(1) When retrains are performed. At 2400 bps operation or higher,
the Modem may lose synchronization with the incoming line signal.
Retraining is an adjustment process performed when one of the
modems detects possible line problems which threaten data
integrity.


(2) When in the command mode following an escape sequence. The
Modem will continue to acknowledge and accept data. This data is
stored until the Modem is returned to data mode and then the data
is delivered. In non-MNP mode, any data received while the Modem is
in command mode is lost.

Class 5 Data Compression. Class 5 may be enabled or disabled by
using the AT%Cn command. During an MNP 5 connection, the Modem
compresses data into tokens before transmitting to the remote
modem, and de-compresses the data before it is received.

Programmable Inactivity Timer. You can specify the length of time
the modem will wait before disconnecting when no data is sent or
received. In MNP mode, this timer is reset whenever data is sent or
received. Use the AT\Tn command to set this value where N is a
number between 0 and 42 minutes.

Data Transfer. You may operate MNP in either block or stream mode.
In stream mode, MNP sends data frames in varying lengths depending
on the amount of time between characters being received. Stream
mode is selected with the AT\Ln command.

In block mode, MNP sends fixed data frames of 64, 128, 192, or 256
characters in length. Your communications software must support the
use of block mode.


4.3 AT Commands for MNP Operation

The 14.4K Modem supports all of the preceding classes. The
following AT Commands apply to the MNP protocol:

AT\An Maximum MNP Block Size
AT\Bn Transmit Break
AT\Gn Modem to Modem Flow Control
A\Kn Break Control
AT\Ln MNP Block Transfer Control
AT\Nn Operation Mode Control
AT\Wn Split Speed Operation
AT\Z Switch to Normal Mode
AT*H MNP Link Negotiation Speed

Default selections are highlighted.

Command: AT\An

Maximum MNP Block Size. Use this command to transmit smaller blocks
of data in a reliable data link connection.

0 = set maximum block size to 64 characters.
1 = set maximum block size to 128 characters. (DEFAULT)
2 = set maximum block size to 192 characters.
3 = set maximum block size to 256 characters.


Command: AT\Bn

Transmit Break. When this command is entered during a non-MNP
connection, a break signal is sent to the remote modem.
The length of the break is 100 times the n parameter (1-9) in
milliseconds. The default is 3.

Command: AT\Gn

Modem to Modem Flow Control. Enables or disables modem to modem
flow control during a normal mode connection. This command is
ignored when error correction is selected.

0 = Disables flow control (XON/XOFF) (DEFAULT)
1 = Enables flow control (XON/XOFF)

Command: AT\Kn

Break Control. Determines the modem response when a BREAK is
received from the DTE or the remote modem. The values of the
parameters vary based on the three following conditions:

(1) When a break is received from the DTE during NORMAL or
MNP mode:

0, 2, 4 = modem enters command mode without sending a
break to the remote modem.
1 = modem clears the terminal and modem buffers and
sends a break to the remote modem.
3 = modem does not clear the buffers, but sends a break
to the remote modem.
5 = modem sends a break to the remote modem in
sequence with any transmitted data. (DEFAULT)

(2) When a break is received from the remote modem during NORMAL
mode:

0, 1 = modem clears the terminal and modem buffers and
sends a break to the local DTE.
2, 3 = modem does not clear the buffers but sends a break
to the local DTE.
4, 5 = modem sends a break in sequence with any data being
buffered. (DEFAULT)

(3) When a break is received from the DTE during DIRECT MODE:

0, 1, 3 = modem sends a break to the remote modem and enters
command mode.
2, 4, 5 = modem sends a break to the remote modem.
(DEFAULT)




Command: AT\Ln

MNP Block Transfer Control. Determines whether or not the modem
will use block or stream mode for MNP link.

0 = uses stream mode for MNP link connections (DEFAULT)
1 = uses block mode for MNP connections

Command: AT\Nn

Error Correction Operating Mode. Selects the operating mode the
modem uses while connected.

0 = NORMAL (speed buffering) mode.
1 = DIRECT (pass-through) mode.
2 = RELIABLE LINK mode. Specifies error correction for
the modem-to-modem connection
3 = AUTO-RELIABLE LINK mode. Attempts error-correction
connection but will fall back to normal mode if unable to
establish an MNP link.
4 = LAPM error correction mode.
5 = MNP error correction mode


Command: AT\Wn

Split Speed Operation. Supports a split-speed DCE/DTE interface for
applications which require a transmit speed of 75bps and receive
speed of 1200bps at the DTE interface.

0 = disables (DEFAULT)
1 = enables

Command: AT*H

MNP Link Negotiation Speed. Controls the connection speed for link
negotiations.

0 = link negotiation occurs at the highest supported speed.
(DEFAULT)
1 = link negotiation occurs at 1200bps.


4.4 S-Register Values for MNP Operation

The following S-Registers apply to the MNP protocol.

S36 LAPM Failure Control
S38 Delay Before Forced Connect
S40 Bit-Mapped
S46 Data Compression Control
S95 Extended Result Codes



S36 0-7 7 LAPM Failure Control

Description: Indicates what happens during a LAPM failure. These
fallback options take effect immediately upon connection if
S28=148. If an invalid number is entered, the number is accepted
into the register, but S36 acts as if the default value has been
entered.


0 = modem disconnects
1 = modem stays online; establishes a direct mode connection.
2 = Reserved.
3 = modem stays online; establishes a normal mode connection.
4 = attempts MNP connection; if it fails, modem disconnects.
5 = attempts MNP connection; if it fails, establishes a
direct mode connection.
6 = Reserved.
7 = attempts MNP connection; if it fails, establishes a
normal mode connection. (DEFAULT)

S38 0-255 20 Delay Before
Forced Disconnect

Description: This register specifies the delay between the modems
receipt of the ATH command to disconnect.

S40 Bit Mapped. Bit Mapped
Registers (for MNP)

Description: Indicates the status of command options.

Bit 0 MNP Extended Services
0 = disabled (-K0)
1 = enabled (-K1) (DEFAULT)

Bit 1 Power Level Adjustment for Cellular Use
()Mn)
0 = auto adjustment ()M0) (DEFAULT)
1 = force adjustment ()M1)
Bit 2 MNP Link Negotiation Speed (*H1)
0 = highest speed (*H0) (DEFAULT)
1 = 1200 bps (*H1)
Bits 3-5 Break Handling (\Kn)
0 = \K0 1 = \K1
2 = \K2 3 = \K3
4 = \K4 5 = \K5 (DEFAULT)
Bits 6-7 MNP Block Size
0 = 64 chars. (\A0) 1 = 128 chars. (\A1)
2 = 192 chars. (\A2) (DEFAULT)
3 = 256 chars. (\A3)

S46 136, 138 Data Compression
Control


136 = error correction protocol with no compression

138 = error correction protocol with compression
(DEFAULT)

Description: Controls selection of compression.

S95 none Extended Result Codes


Bit 0 = CONNECT CODE indicates DCE speed
instead of DTE speed.
Bit 1 = Append /ARQ (automatic repeat request)
to verbose CONNECT XXXX result code if
protocol is other than none.
Bit 2 = Enable CARRIER XXXX result code.
Bit 3 = Enable PROTOCOL XXXX result code.
Bit 5 = Enable COMPRESSION result code.
Bits 4, 6, and 7 are reserved.


Description: The bits in this register can be set to override some
of the ATWn command options.
































Section Five: Error Correction: V.42/V.42bis

5.1 Introduction


V.42 and V.42bis are two different communication protocol standards
set by CCITT (Consultative Committee on International Telegraph and
Telephone).

V.42 is the CCITT standard for error correction in modems and is
normally found in modems that are 2400bps or faster. V.42 supports
LAPM and MNP 4 and is therefore compatible with modems using MNP 4.

The V.42 specification is a standard that supports one of the
Microcom MNP 2-4 error correction protocols or the LAPM error
correction protocol.

The V.42bis specification is a data compression standard that
requires the LAPM error correction protocol, as well as providing
data compression up to twice as fast as the MNP 5 data compression
standard.

MNP 5 is another data compression standard that requires the MNP 4
error correction protocol. It is not compatible with V.42bis and is
slower than the V.42bis data compression standard.

Detection. Immediately after the initial handshake , the
communicating modems exchange a sequence of detection patterns to
verify that both sides support the error correction technique.

Negotiation. The communicating modems exchange configuration
information.

If the detection phase fails, or negotiation does not achieve the
desired connection type, the modem can do one of the following:

* hang up
* fall back to MNP
* fall back to a standard asynchronous mode

In this case, you would use register S36 for Negotiation Fallback
and/or S48 for Negotiation Action. Because MNP does not support a
detection phase, you must select MNP 4 as a forced fallback with
S36 and S48. The following S registers are used for V.42 LAPM
operation:

Register Description
S36 V.42 Negotiation Fallback
S38 Delay Before Forced Connect
S41 Bit-Mapped Registers
S46 Protocol Selection
S48 V.42 Negotiation Action
S82 Break Handling
S86 Connection Failure Cause Code
S95 Extended Results Code

These registers are described in the balance of this section.


5.2 S Registers


5.2.1 V.42 Negotiation Fallback (S36)

Register S36 specifies allows you to indicate what action to take
when a desired connection cannot be made. The options are:

S36=0 Modem hangs up.

S36=1 Modem stays on-line and a direct mode connection is
established. When running in direct mode, no flow control
characters are recognized or transmitted. Flow control is when a
receiving buffer tells the transmitting source to start and stop
transmission. Direct mode is often used for compatibility with
older style modems.

S36=2 Reserved.

S36=3 Modem stays on-line and a normal mode connection is
established. Normal mode (or speed buffering) allows the modem to
send and receive at a speed different from the speed of the
physical, or modem to modem connection.

S36=4 If S Register 48 is 128, an MNP connection is attempted; if
it fails, the modem disconnects.

S36=5 If S Register 48 is 128, an MNP connection is attempted; if
it fails, a direct mode connection is established.

S36=6 Reserved.

S36=7 If S Register 48 is 128, an MNP connection is attempted; if
it fails, a normal mode connection is established. (DEFAULT)


5.2.2 Delay Before Forced Connect (S38)

S38 allows the following:

S38 = 0-255 Specifies the delay between the modems receipt of
the ATH command to disconnect (20 is the default).


5.2.3 Protocol Selection (S46)

S46 allows the following:

S46=136 Activates LAPM protocol with NO V.42bis compression.
(DEFAULT)

S46=138 Activates LAPM protocol WITH V.42bis compression.

NOTE: In addition to V.42bis, the modem also implements MNP 5 data
compression. V.42bis is used only with LAPM; MNP 5 is used only
with MNP 4.

5.2.4 V.42 Negotiation Action (S48)

Negotiation determines the capability of the remote modem. If the
capabilities of the remote modem are known and negotiation is
unnecessary, you can bypass this function.

S48=7 Enables negotiation. (DEFAULT)

S48=0 Disables negotiation. This bypasses the negotiation and
detection phases and proceeds with LAPM.

S48=128 Disables negotiation. This bypasses the negotiation and
detection phases and proceeds at once with the fallback options
specified in S Register 36. This option can be used to force MNP.

5.2.5 Bit-Mapped Registers

These registers control compression selection, retraining, flow
control, and block mode control.

Bits 0,1 = Compression selection
Bit 2 = Auto retrain
Bit 3 = Modem to Modem Flow Control
Bit 4 = Block Mode Control
Bits 5-7 are reserved

5.2.6 Break Handling (S82)

LAPM specifies three methods of break signal handling:

* in sequence, expedited, or destructive

S82=128 In sequence. Modem sends a break in sequence with any
transmitted data; data integrity is maintained both ahead of and
after the break. (DEFAULT)

S82=3 Expedited. Modem sends a break immediately; data
integrity is maintained both ahead of and after the break.

S82=7 Destructive. Modem sends a break immediately; data being
processed by each modem at the time of the break is destroyed.

5.2.7 Connection Failure Cause Code (S86)

When the modem issues a NO CARRIER result code, a failure code is
written to register S86. S86 records the first event that
contributes to a NO CARRIER message. The result code definitions
are as follows:

S86=0 Normal disconnect; no error occurred.

S86=4 Loss of carrier.

S86=5 V.42 negotiation failed to detect an error correction
modem at the other end.

S86=9 The modems could not find a common protocol.

S86=12 Normal disconnect initiated by remote modem.

S86=13 Remote modem does not respond after 10 re-transmissions
of the same message.

S86=14 Protocol violation.

5.2.8 Extended Results Code (S95)

You can set the bits in this register to override some of the ATWn
command options. A bit to set to 1 in this register enables the
corresponding result code regardless of the ATWn setting.

Bit 0 = CONNECT result code indicates DCE speed instead of DTE
speed.
Bit 1 = Append/ARQ to verbose CONNECT XXXX result code if
protocol is not NONE.
Bit 2 = Enables CARRIER XXXX result code.
Bit 3 = Enables PROTOCOL XXXX result code.
Bit 5 = Enables COMPRESSION result code.
Bits 4, 6, 7 are reserved.


5.3 AT Commands for Error Correction (V.42/V.42bis)

The following AT commands apply to the V.42/V.42bis protocol:

AT%Cn Compression Control
AT%En Auto Retrain
AT%Fn Split-Speed Direction Select
AT%L Report Received Signal Level
AT%Q Report Line Signal Quality


Command: AT%Cn

Compression Control. Determines whether or not modem will use data
compression.

0 = disables data compression
1 = enables MNP5 data compression negotiation
2 = enables V42bis data compression
3 = enables both V.42bis and MNP5 data compression (DEFAULT)


Command: AT%En

Auto-retrain. Determines whether or not the modem automatically
monitors the line quality and requests a retrain when necessary.

0 = disables line quality monitor auto-retrain (DEFAULT)
1 = enables line quality monitor auto-retrain
2 = enables line quality monitor auto retrain and auto fall
back/forward.


Command: AT%Fn

Split-Speed Direction Select. Determines which direction (transmit
or receive) has the 75bps channel and which has the 7500bps
channel. Valid only if the \W1 command has been entered.

1 = selects 75Tx/1200Rx
2 = selects 1200Tx/75Rx (DEFAULT)


Command: AT%L

Report Received Signal Level. Possible values are:

009 = -9 dBm, 010 = -10dBm, etc. all the way to 043 (-43 dBm)

Line signal and noise are determined by the unit of measurement dBm
(decibel referenced to one milliwatt). To arrive at a signal/noise
ratio, the noise level is subtracted from signal level in dBm.


Command: AT%Q

Report Line Signal Quality. Returns a high-order byte of the
calculated EQM (eye quality monitor). This can range from 0 to 255.
When the value is 8 or greater, the modem will automatically
retrain if enabled by the AT%E1 command. The value for a normal
connection ranges from 0 to 2 and approaches 8 for a progressively
poorer connection. Returns an OK result code.

000 to 007 = no retrain
008 to 255 = retrain performed if enabled by %E1.











Section Six: V.32/V.32bis Operation

These CCITT protocols allow for high-speed data transmission and
reception up to a maximum throughput speed of 57,600 bps (with
V.42bis data compression). The 14.4Kbps modem is upwardly
compatible to both of these high-speed modulation protocols.

The V.32 CCITT standard enables full-duplex 9600 bps asynchronous
transmission to occur synchronously over the switched telephone
network and can attain throughput rates of 38,400 bps when combined
with V.42 error control. The V.32bis modulation protocol extends
the 9600 bps capability of V.32 to 14,400 bps while remaining
compatible with V.32 modems.

Possible modem to modem connection speeds are as follows:


V.32 4800 bps
9600 bps

V.32bis 14.4Kbps
12K bps
7200 bps


The ATNn command (Modulation Handshake) determines whether or not
the modem allows only particular connections, or automatically
detects a remote modems desired connection.

ATN1 (default) allows communicating at any speeds supported by both
modems.

Entering the command ATN0 requires that the speed of the connection
be that specified by the value of S-Register 37 (see p. 53). If
that value were not one supported by V.32, communication would not
be possible.


















Section Seven: Diagnostics

The 14.4Kbps modem includes several tests which evaluate the
operation of the modem, its connection to the local DTE, and the
communications link between the local and remote modems. Use of
these tests requires setup of internal registers and may also
require the use of two modems and a central office line
simulator. A thorough knowledge of modem operation and registers is
needed for their use.


7.1 Local Analog Loopback Test

This test verifies the path between the local modem and the PC.

1. Set the DTE speed from 1200 to 14,400 bits per second. If the
speed is less than 1200 or greater than 14,400 the test WILL NOT
operate and a result code of ERROR will be generated if any tests
are attempted.

2. Make sure the modem is in command mode (no connection made).

3. Issue an AT&Q0 command to the modem. This sets the modem to the
direct mode.

4. Set the timer register (S18) for desired test time (in seconds).
Example: ATS18=10 provides for a 10 second test.

5. To begin the test, type AT&T1 [ENTER]. The modem should respond
with a CONNECT message.

6. After the number of seconds specified in S18, the modem will
terminate the test and respond with OK.


7.2 Local Analog Loopback Test with Self-Test

This test verifies the integrity of the local modems transmit and
receive circuits.

1. Set the DTE speed from 1200 to 14,400 bits per second. If the
speed is less than 1200 or greater than 14,400 the test WILL NOT
operate and a result code of ERROR will be generated if any of the
tests are attempted.

2. Make sure the modem is in command mode (no connection made).

3. Issue an AT&Q0 command to the modem. This sets the modem to the
direct mode.

4. Set timer register (S18) for desired test time (in seconds).
Example: ATS18=10 provides for a 10 second test.

5. To begin, type AT&T8 [ENTER]. The modem responds with OK.

6. After the number of seconds specified in S18, the modem should
respond with 000 (meaning 0 errors were found during the self
test).


7.3 Remote Digital Loopback Test

1. Set the DTE speed from 1200 to 14,400 Bits per second. If the
speed is less than 1200 or greater than 14,400 the test WILL NOT
operate and a result code of ERROR will be generated if the test is
attempted.

The baud rate is also limited to the highest baud rate supported by
the telephone line (14,400 is possible if the telephone line is
without distortion and noise free). If the telephone line has
problems, bring the baud rate down to 9600 or 2400. If the line
quality is too poor, use a line simulator to run this test.

2. Issue an AT&Q0 command to the local modem. This sets the modem
to the direct mode.

3. Issue an AT&Q0 command to the remote modem, also setting it to
the direct mode.

4. Issue an AT&T4 to the remote modem. This instructs the remote
modem to grant a request for a remote digital loop back test.

5. Issue an ATS0=1 to the remote modem which allows it to
auto-answer the incoming call.

6. Set the timer register (S18) of the local modem for desired test
time (in seconds). Example: ATS18=10 provides for a 10 second
test.

7. Issue a dial command to the local modem to instruct it to call
the remote modem. Wait until the two modems have established a
connection.

8. Type the escape sequence +++ to revert to command mode. The
modem will respond with OK.

9. To start the test, type AT&T6 [ENTER]. The modem will return a
CONNECT response if the loopback data link has been successfully
completed, and an ERROR response if the link has failed. If a
CONNECT response was received, key in a text message and it will
echo on the screen.


7.4 Remote Digital Loopback Test with Self-test

1. Set the DTE speed from 1200 to 14,400 bits per second. If the
speed is less than 1200 or greater than 14,400 the test WILL NOT
operate and a result code of ERROR will be generated if the test is
attempted.

The baud rate is also limited to the highest baud rate supported by
the telephone line (14,400 is possible if the telephone line is
without distortion and noise free). If the telephone line has
problems, bring the baud rate down to 9600 or 2400. If the line
quality is too poor, use a line simulator to run this test.

2. Issue an AT&Q0 command to the local modem. This sets the modem
to the direct mode.

3. Issue an AT&Q0 command to the remote modem, also setting it to
the direct mode.

4. Issue an AT&T4 to the remote modem. This instructs the remote
modem to grant a request for a remote digital loop-back test with
self test.

5. Issue an ATS0=1 to allow the remote modem to auto-answer the
incoming call.

6. Set timer register (S18) of the local modem for desired test
time (in seconds). Example: ATS18=10 provides for a 10 second
test.

7. Issue a dial command to the local modem to instruct it to call
the remote modem. Wait until the two modems have established a
connection.

8. Type the escape sequence (+++) to revert to the command mode.
The modem will respond with OK.

9. Type AT&T7 [ENTER] to initiate the remote digital loopback test.
The local modem will send a test pattern to the remote modem. This
pattern will not be visible on the screen.

10. The modem will then send a three-digit value, indicating the
number of errors detected during testing. If the result is 000, no
errors were found.


















Section Eight: Troubleshooting

This section lists the most common problems that may be encountered
and their possible solutions.


SYMPTOM: POSSIBLE REMEDY:

No dial tone. Check the following:

Verify that you have the cables plugged in
correctly as instructed in Section One.

Connect a telephone set directly to the
wall jack and check for dial tone. If no
dial tone is heard, the telephone line is
not working. Contact the telephone
company.


No response
when you type in
AT commands. Check the following:

There may be a conflicting port address.
Re-configure the modem COM address.
(INTERNAL ONLY)

Verify that the communication software is
set for the same COM address.

Your RS-232 cable connection (EXTERNAL
ONLY).


AT commands are
not visible. Check the following:

Make sure the echo command is set to off.
Change to echo with the ATE1 command.


After data connection
is established, data is
displayed as garbled
characters. Check the following:

Make sure the local and remote modem
configurations are compatible.

Verify that both modems are operating with
the same settings, speed, data, parity,
and stop bits.

The software may not be set for correct
terminal emulation. Configure software to
correct type. ANSI terminal emulation is
most commonly used.

Turn off your modem (EXTERNAL), exit, and
re-run your communications software.

Power down your system (INTERNAL) and
re-run your communications software.


A slowdown is noticed
when running multi-
tasking software.
When multi-tasking with fast machines
(e.g., 386DXs, 486/DXs), the CPU will
easily handle a high number of interrupts.
With slower CPUs such as 286 and 386SX
machines, a slowdown can occur.



































Appendix A: How to Set Bit-Mapped Registers

To set or change bit-mapped registers requires a sound working
knowledge of binary notation and should not be undertaken casually.
Bit-mapped S-Register values are calculated as follows. Each bit
(0-7) has a corresponding decimal value as shown below. Of the bit
is ON, it has that corresponding value; if the bit is OFF, its
value is zero.

Bit Decimal
0 1
1 2
2 4
3 8
4 16
5 32
6 64
7 128

Some bit-mapped registers combine bits which make calculating
values even more complex. Example: if bits 3 and 4 were combined to
offer four options ((0-3), the value would be calculated this way:

BIT 4 (16) BIT 3 (8) OPTION VALUE

0 (0) 0 (0) 0 0
0 (16) 1 (8) 1 24 (16+8)
1 (32) 0 (16) 2 48 (32+16)
1 (48) 1 (24) 3 72 (48+24)

Now, let's try a real example. Register S14 contains a set of
bit-mapped registers for echoing commands, result code display,
word/number responses, dial method, and answer/originate operation.
On the next page are the default settings and corresponding values
along with default settings.

Value(Bit)

128(7) 64(6) 32(5) 16(4) 8(3) 4(2) 2(1) 1(0) value
| | | | | | | |____ ignored 0
| | | | | | |_________ 0= no echo
| | | | | | 1= echo 2
| | | | | |______________ 0= send resp.
| | | | | 1= no send 0
| | | | |___________________ 0= send #
| | | | 1= send word 8
| | | |________________________ reserved 0
| | |_____________________________ 0= touch tone 0
| | 1= pulse
| |__________________________________ reserved 0
|_______________________________________ 0= answer
1= originate 128

The S-Register bit-mapped value would be 138 (2+8+128)

Appendix B: Technical Specifications

Modem Data Rate: 14.4K, 12K, 9600, 7200, 4800,
2400, 1200, or 300 bps

Fax Data Rate: 14.4K, 9600, 7200, 4800, 2400
bps.

Compatibility: Modem Modulation
Protocols CCITT:
Bell 103, 212A
V.32bis, V.32, V.42bis, V.42, V.22,
and V.21.

Fax Modulation Protocols
CCITT: V.17, V.29, V.27 ter, and
V.21

Operation: Asynchronous operation (MNP 3:
synchronous)
Automatic format and/or speed sensing.
Tone or Pulse dialing
Programmable speaker volume control--recognizes
busy signal, ringing, no answer, and no
dial-tone status.

Diagnostics: Local/remote digital and analog loopback.
Automatic power-on self-test.

Physical and Electrical Characteristics

Size: 8" x 4 3/8" (INTERNAL); 5 1/2" x 5" x 2" (EXTERNAL)
Power: 500 mA@ 5V(INTERNAL); 120V AC@ 100mA (EXTERNAL)
8- or 16-bit interface (INTERNAL)
2 RJ-11 modular phone connectors.
RS-232 serial cable (EXTERNAL)
Compatible with IBM PC systems (ISA and EISA).


















Appendix C: Compliance Information

FCC Statement

"This device complies with part 15 of the FCC rules. Operation is
subject to the following two conditions:

(1) This device may not cause harmful interference.
(2) This device must accept any interference received including
interference that may cause undesired operation.

THIS UNIT COMPLIES WITH FCC PART 68 AS OF DATE OF MANUFACTURE.

This equipment has been tested and found to comply with the limits
for a Class B digital device, pursuant to Part 15 of FCC rules.
These limits are designed to provide reasonable protection against
harmful interference in a residential installation. This equipment
generates, uses, and can radiate radio frequency energy and, if not
installed in accordance with the instructions, 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:

* Re-orient or relocate the receiving antennae.
* Increase the separation between the equipment and the receiver.
* Connect the equipment into an outlet on a circuit different from
that to which the receiver is connected.
* Consult the dealer or an experienced radio/TV technician for
help.

Note: This unit was tested with shielded cables on the peripheral
devices. Shielded cables must be used with the unit to insure
compliance.

Note: The manufacturer is not responsible for any radio or TV
interference caused by unauthorized modifications to this
equipment. Such modifications could void the user's authority to
operate the equipment."

Notification to the Telephone Company

Notification to the telephone company is no longer required prior
to connecting the registered equipment but upon request from the
telephone company the user shall tell the telephone company which
line the equipment is connected to as well as the registration
number and the ringer equivalence of the registered protective
circuitry. In most, but not all areas, the sum of all RENs should
be 5.0 or less. The FCC Registration number and Ringer Equivalence
number are printed on the main chip in the center of the internal
modem board, or on the underside of the external modem.

Malfunction of the Equipment

In the event that the MODEM should fail to operate properly, the
customer shall disconnect the equipment from the telephone line to
determine if it is the customer's equipment which is not working
properly, or if the problem is with the MODEM, the user shall
discontinue use until it is repaired. In the event service is
needed the user should contact the vendor from whom you purchased
the MODEM.

Telephone Connection Requirements

Except for telephone company-provided ringers, all connections to
the telephone network shall be made through standard plugs and
standard telephone company-provided jacks, or equivalent, in such
a manner as to allow for easy and immediate disconnection of the
terminal equipment. Standard jacks shall also be arranged that, if
the plug connected thereto is withdrawn, no interference to the
operation of the equipment at the customer's premises which remains
connected to the telephone network, shall occur by reason of such
withdrawal.

Incidence of Harm

Should terminal equipment or protective circuitry cause harm to the
telephone network, the telephone company shall, where practical,
notify the customer that temporary discontinuance of service may be
required; however, where prior notices are not practical, the
telephone company may temporarily discontinue service if such
action is deemed reasonable in the circumstances. In the case of
such temporary discontinuance, the telephone company shall promptly
notify customers and will be given the right to bring a complaint
to the FCC if they feel the disconnection is not warranted.


Changes in Telephone Company Equipment or Facilities

The telephone company may make changes in its communications
facilities, equipment, operations, or procedures, where such action
is reasonably required and proper in its business. Should any such
changes render the customer's terminal equipment incompatible with
the telephone company facilities, the customer shall be given
adequate notice to make modifications to maintain uninterrupted
service.

General

The FCC prohibits customer-provided terminal equipment be connected
to party lines or to be used in conjunction with coin telephone
service.

Installation
The MODEM is equipped with a USOC RJ-11 standard miniature modular
jack and is designed to plug directly into a modular jack.


DOC Compliance Statement (Canada)

The Canadian Department of Communications label identifies
certified equipment. This certification means that the equipment
meets certain telecommunications network protective operational and
safety requirements. The Department 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. In some cases, the
company's inside wiring associated with a single line individual
service may be extended by means of a certified connector assembly
(telephone extension cord). 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 malfunction, 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.

The Load Number (LN) assigned to each terminal device denotes the
percentage of the total load to be connected to a telephone loop
which is used by the device to prevent overloading. The termination
on a loop may consist of any combination of devices subject only to
the requirement that the total of the load numbers of all the
devices does not exceed 100. The Load number appears on either the
lower inside portion of the modem's metal bracket (internal) or on
the underside of the external modem.











Glossary of Modem Terminology

A

ALGORITHM. A formula or procedure which employs various methods
defining how data is to be used to give a prescribed result.

ANALOG SIGNAL. Signals which can vary over a continuous range
(e.g., the human voice over conventional telephone lines). Analog
circuitry is more subject to distortion and noise, but it is more
capable of handling complex signals than are digital signals which
can have only discrete values.

ARQ. Automatic ReQuest for retransmission. A type of communications
link where the receiver asks the transmitter to re-send a block of
data when errors are detected.

ANSI. American National Standards Institute. A non-profit, private
industry association which governs most USA-standards setting
agencies.

ASCII. Acronym for American Standard Code for Information
Interchange. ASCII is an ANSI character set. The standard ASCII
character set consists of 128 decimal numbers (0-127) for letters
of the alphabet, numerals, punctuation marks, and common special
characters. The extended ASCII character set extends to 255
characters and contains special mathematical, graphics, and foreign
characters.

ASYNCHRONOUS COMMUNICATION. A method of transmission in which data
is sent one character is sent one bit at a time; also referred to
as serial transmission.


B

BELL STANDARDS. Refers to the domestic modulation protocol
standards developed by the former AT&T Bell Systems such as Bell
103 (300bps transmission) and Bell 212A (1200bps transmission).

BIT-MAPPED REGISTERS. An S-register which contains multiple
bit-oriented values. Example: the value of S22 is the sum of the
bit values which you select (bits 0-1: speaker volume/value: 0-3;
bits 2-3: speaker control/value: 0-3; bits 4-6: limit result
codes/value: 0, 4-6, 7).

BLIND DIALING. An automated process whereby the modem goes off-hook
and dials without waiting for a dial tone. This is prohibited in
many countries.

BLOCK TRANSFER CONTROL. Determines whether or not the modem uses
block or stream mode during an MNP connection. In stream mode, MNP
sends data frames in varying length. Block mode sends fixed data
frames of 256 characters and is selected with the MNP-based \L
command.

BREAK HANDLING. Determines how the modem responds when a BREAK
signal is received from either the DTE (Data Terminal Equipment or
computer/terminal) or the remote modem. This is controlled by the
MNP-based AT extended command \K. A break signal is represented on
the communications line by a steady space signal for a
significant length of time. Break signals may be activated from the
keyboard by pressing the BREAK key or the control (CTRL) and C
keys.


C

CCITT. Consultative Committee for International Telephone and
Telegraph. This advisory organization is part of the ITU
(International Telecommunication Union) which is an agency of the
United Nations.

COMMAND MODE. The modem is in command mode when it is turned on or
reset, when it loses its connection to a remote modem, when it is
in on-line mode, or when escape characters (+++) are typed. To
transmit data, the modem must be in data mode. The modem does not
transmit data when in command mode.

COMMUNICATIONS PROTOCOL. A set of procedures which controls how a
data communications network operates.


D

DCD. Data Carrier Detect. Indicates to the terminal device that the
modem is receiving a valid carrier signal from a remote modem. The
carrier is a tone at a specified frequency.

DCE. Data Communications Equipment. The local and/or remote modem.
A DCE is usually connected to a DTE.

DTE. Data Terminal Equipment. The computer or terminal, either
local (yours), or the remote (the one you're communicating with).
A DTE is usually connected to a DCE.

DTR. Data Terminal Ready. The computer issues this signal to the
attached modem indicating that it is ready to receive data.

DATA COMPRESSION. A technique that examines transmitted data for
redundancy and replaces strings (groups) of characters with special
codes which the receiving modem interprets and restores to its
original form. Transmission of compressed data results in shorter
connect times and hence cost savings for connect charges.
Data compression is sometimes called source encoding.

DATA MODE. The modem is in data mode when a connection has been
established with a remote modem and sends a CONNECT response
confirming the connection. User data may then be transmitted or
received.

DIAL MODIFIER. Dial modifiers are special characters appended to
the ATD command which instruct the modem how to place a call.

DIGITAL SIGNAL. A discrete signal which can only take on one of
several (usually only two) discrete levels in contrast to analog
signals which can take a continuous range of levels.


E

ERROR DETECTION AND CORRECTION. The transmitting modem attaches a
special pattern (called a frame check sequence) calculated
according to a prescribed algorithm from user-defined data to the
end of a block of data. The receiving modem performs the same
algorithm and compares it to the one with the transmitted data. If
these match, then the block of data has been received correctly. If
not, the block of data is re-transmitted until no errors are
detected.

ESCAPE SEQUENCE. Also referred to as the escape command. This
special command is entered as three plus symbols (+++) and places
the modem in command mode and interrupts user data transmission,
but does not terminate the data connection. This allows the
entering of commands while the connection is maintained.

EXTENDED AT-COMMAND. Extended commands were developed to provide
greater functionality and control over modem operations than is
available from the basic AT command set.


F

FAX MODE. The modem is in fax mode when, through use of fax
communications software, it can send and receive faxes, print and
display fax files, convert files to fax-files, and set certain
fax-related features. Note: the modulation protocol used by the
modem in fax mode is also different from the usual data mode
modulation.

FLOW CONTROL. Compensates for the difference between the rate at
which data reaches a device and the rate at which the device
processes and transmits. This is controlled by the extended AT
command &K. The two common types of flow control are RTS/CTS
signaling (a hardware based method, employing an electrical signal)
and XON/XOFF (a software-based method using standard ASCII control
characters to pause or resume transmission).

FULL-DUPLEX. Two-way simultaneous transmission between modems,
which may occur via a four-wire circuit on a leased line, or with
a two-wire connection when the frequency bandwidth is divided into
two distinct channels, or when echo cancellation is employed (e.g.,
Bell 103, 212, and V.22 use frequency division, while V.32 uses
echo cancellation.


G

GUARD TONE. Guard tones are used in the United Kingdom and other
countries. This requires that the modem transmit an 1800-Hz tone
after it sends an answer tone. The guard tone is controlled by the
&G command. Guard tones are not used in the U.S.A.


H

HALF-DUPLEX. Signal flow in both directions, but only one way at a
time with each modem alternating between send and receive.

HAYES-COMPATIBLE. Hayes Microcomputer Products, Inc. developed the
AT command set which has become a de facto industry standard. Hayes
commands are always initiated with an AT (attention code) prefix.

HOOK FLASH. The dial modifier ! causes the modem to go on-hook
(hang-up) for one-half second. Also controlled by the ATH command.


L

LAPM. Link Access Protocol Modem. A V.42 ARQ type of error
correction protocol which is controlled by S-Register 46, where
LAPM may be activated with or without V.42bis data compression.

LEASED LINE. Also referred to as a private line. A leased line is
obtained from a communications company (carrier) to provide a
transmission medium between two points. The line consists of a
permanent dedicated circuit between two points, or to set of
previously arranged points. The cost of the line is usually based
on the distance between locations. This is in contrast to switched
or dial-up lines, which can be connected to any point on the
network.

LINE MODULATION. The means by which a carrier is varied to
represent a signal carrying information. In a modem, the users
digital data is used to modulate the modem's transmitters carrier
or carrier to allow the digital signal to be carried over analog
facilities.

LONG SPACE DISCONNECT. Determines whether or not modem disconnects
when it receives a continuous break from a remote modem. Controlled
by the ATY command.

LOOPBACK TESTS. There are four types of loopback tests which are as
follows: (1) the local digital loopback tests the operation of the
DTE, including whether or not data is leaving the terminal or
computer port; (2) the local analog loopback tests the digital and
analog circuits of the modem; (3) the remote digital loopback
checks the operating condition of the line and remote modem; (4)
the remote analog loopback tests the line to the remote modem.


M

MNP. Microcom Networking Protocol. A series of data communications
protocols developed by Microcom for full-duplex, error-free
communications.

MAKE/BREAK RATIO. The &P command controls the ratio of the off-hook
(make) to on-hook (break) interval used by the modem when it pulse
dials. &P0 selects a 39%/61% make/break ratio for use in the U.S.
&P1 selects a 33%/67% make/break ratio for use in the United
Kingdom and Hong Kong.

MODULATION HANDSHAKE. Also referred to as Automode Enable and is
controlled by the ATN command. This determines whether or not the
modem must connect at a particular speed, or allow connection at
any speed supported by both modems.


N


NEGOTIATION FALLBACK. Controlled by S-Register 36 as part of the
V.42 protocol. Setting this register indicates what action to take
when a desired connection cannot be made (e.g., hang-up, direct
mode connect, normal mode connect).

NON-VOLATILE RAM. Also NVRAM. Random access memory whose data is
retained when power is turned off. This is especially useful for
modems to store user-defined default configuration settings. These
settings would be loaded into modem RAM at power-up.


O

ON-LINE STATE. Same as data mode. To transmit or receive data, the
modem must be in the on-line state. When placing a call, the modem
is put on-line with the dial command.


P

PBX. Private Branch Exchange. A telephone switch at a customer
site.

PULSE DIALING. Also referred to as rotary dialing, i.e., dialing
with the older-style rotary dial wheel. The dial modifier ATP sets
the modem to pulse dialing, which is the default method as opposed
to tone dialing (push-button touch-tone) which is enabled with ATT.
All telephone exchanges will accept older-style pulse dialing and
most exchanges will accept modern tone-dialing. Tone dialing is
faster and more reliable since mechanical relays and their inherent
failure mechanisms are avoided.


R

RESULT CODE. A response sent by the modem after executing a
command. The response reports the modems status or the progress of
a call and can take the form of either digits (numeric) or words
(verbose). Issuing a V1 command enables word responses. A V0
(V-zero) command enables numeric responses. The Q1 command
disables their use entirely. Example: OK (word), or 0 (numeric)
indicates that the modem successfully executed a command.

RETRAIN. An adjustment process performed when one of the modems
detects signal distortion or line noise which threaten data
integrity.

RTS/CTS. Request to Send/Clear to Send. RTS and CTS are two
control signal lines between the modem (DCE) and terminal (DTE)
which allow the terminal to control the flow of information. See
also flow control.


S

SLEEP INACTIVITY TIMER. Determines the length of time the modem
operates in normal mode with no activity before entering low-power
sleep mode.

SPLIT-SPEED DIRECTION. Determines which direction (transmit or
receive) has the 75bps channel and which has the 1200bps channel,
but is only active if the \W command is set to 1. Used with V.23
modulation only.

STANDARD AT-COMMAND. The basic AT command set, originated by Hayes
Microcomputer Products, Inc.

SYNCHRONOUS CLOCK SOURCE. Applies to synchronous modem operations
and is set with the &X command. The command specifies the clocking
source referred to as the transmit signal element timing. This can
be controlled by either the modem or the terminal.

SYNCHRONOUS COMMUNICATIONS. A method of transmission in which data
bits are sent continuously at the same rate under the control of a
fixed frequency clock signal.


T

TOUCH-TONE DIALING. Push-button tone dialing as used on
contemporary phone sets. The dial modifier ATT sets the modem to
tone mode. Tone dialing is faster and more reliable than
older-style pulse dialing.


X

XON/XOFF. XON and XOFF are the names of two different control
characters. See also flow control.


Acknowledgements

The Complete Modem Reference. Gilbert Held. John Wiley & Sons, Inc.
1991.

Upgrading and Repairing PCs. (Second Edition). Que Corporation.
1992.