Copyright: Copyright 1993  Intel Corporation


Contents
ATHELP:  Intel AT Command Online Manual

Introduction to AT commands

Help on using help

About ATHELP

AT commands - alphabetical list

AT commands - by functional group

S registers

Configuration parameters

Result codes - alphabetical list

Result codes - numerical list

How to:

Answer a call

Control speaker volume

Contact Intel customer support

Dial phone numbers

Negotiate a normal/reliable/auto-reliable connection

Restore/write/view a configuration profile

Set echo on/off


Initialization strings

Most communications software supports an initialization string, which is an AT command line.

The initialization string sets up (or initializes) the modem so it can negotiate and connect with a remote modem.  Just before the communications software dials the phone, it uses the initialization string.  The communications software stores the initialization string and uses it every time it dials.

Your modem negotiates a connection in two phases:  first speed, and then error control and data compression.  Some modems that don't support error control and data compression interpret the second negotiation as the beginning of the data transmission.  They wait for more data without responding.  You can turn off error correction before your call and eliminate the second negotiation phase by entering this command:

AT\N0

If you dial mainframes or minicomputers, you might need a different initialization string than the default settings.  Ask your system administrator for the initialization string that works with your system.

____________
See also

Attention code

Example of an AT command line

Steps for entering AT commands

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression


Steps for Using the AT Commands
Steps for entering AT commands

Here are the steps for entering an AT command:

1.	Start your communications software.  Be sure your communications software is in terminal mode.  (For information on entering terminal mode, see your communications software's documentation.)

2.	Be sure your modem is in command mode (sometimes called local mode or terminal mode) so that it can interpret your commands.  When you turn on your computer, your modem is automatically in command mode.  If you have recently used the modem to make a call and haven't broken the connection yet, type +++ to escape to command mode.

3.	Now you are ready to type AT commands.  An AT command line starts with the characters AT , which get your modem's attention.  You can type up to 40 command characters in the line, not including the AT or spaces.  See Command Buffer for more information.

4.	Press <Enter> at the end of the line to make the modem act on the commands you just typed.  After completing its tasks, the modem responds by sending a message to your screen, like OK.

____________
See also

Attention code

Example of an AT command line

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


Operating modes

The modem is always in one of two operating modes:

•	Command mode (also called terminal mode or local mode)

•	Online mode (also called data mode)

The modem powers up in command mode.  In this mode, any data you send to the modem is interpreted as one or more modem commands.  The modem tries to execute each command you send it, and it displays a result code on your computer screen that indicates the results of the command.

Using modem commands, you can establish a connection with a remote modem.  When you establish the connection, the modem switches to online mode and relays the data you send to it from your computer to the remote modem.  In online mode, the modem interprets all information sent to it as data.  The only exception is the escape sequence, a special sequence of characters (+++) that returns the modem to command mode without breaking the connection.

Switching between command and online modes

You can switch between command mode and online mode using the escape sequence +++ (to switch from online to command mode) or the O command (to switch from command to online mode).

Both the escape sequence and the O command assume you've already established a connection with a remote modem, either by calling another modem or by answering a call from another modem.

____________
See also

Attention code

Example of an AT command line

Steps for entering AT commands

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


Example of an AT command line

Here is a sample AT command line:

AT  S7=90  V1  DT  1 800 555 3333 <Enter>

AT	gets the attention of your modem.

S7=90	sets register S7 in the modem memory to 90 seconds so the modem waits 90 seconds after dialing.  See S registers for more information.

V1	sets the modem to verbal mode so that the modem displays the results on your screen in words instead of numbers.

DT	tells the modem to dial the following telephone number with tone dialing.

<Enter>	sends the command line to your modem.

You don't need to separate the attention code from the commands or the commands from each other.  For example, you could enter the command line above as follows:

ATS7=90V1DT18005553333 <Enter>

If you make a mistake when you type a command line, you can backspace over any characters except the AT attention code, and retype the line.

____________
See also

Attention code

Steps for entering AT commands

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


The command buffer

As you type a command line, the modem stores the command characters in an area of the modem memory called the command buffer.  The buffer stores up to 40 characters.  The buffer stores only command characters and doesn't store the AT attention code, spaces, or the <Enter> character.

If you type more than 40 command characters on a command line, the modem ignores the command line and displays the ERROR result code.

____________
See also

Attention code

Example of an AT command line

Steps for entering AT commands

Operating modes of the modem

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


General AT commands

These are the general modem commands:

+++	Escape sequence; returns to command mode

A/	Repeats the last command line

AT	Attention code; must precede all commands but A/ and +++

O<n>	Sets conditions to return to online mode


+++ -- Escape sequence

After you've established a connection with a remote modem, you can return to command mode without breaking the connection by typing the escape sequence.

The factory setting for the escape sequence is three plus-sign characters (+++).  When you enter the escape sequence, you don't need to begin with the AT attention code or type <Enter> at the end.

	NOTE:  To change the character used in the escape sequence, change the value in the S2 register.
To prevent the modem from interpreting three consecutive plus signs in the data you send as an escape sequence, the modem requires a guard time for the escape sequence.  The factory setting for the guard time is one second.  So, to be interpreted as a legitimate escape sequence, there must be at least one second before and one second after the escape sequence in which the modem doesn't receive any characters.  Also, you must type the characters of the escape sequence within one second of each other.

	NOTE:  To change the guard time setting, change the value in the S12 register.
The guard time minimizes the chance that the modem will interpret characters in your data stream as escape sequences.  For example, if you transmit a file, it's unlikely that three consecutive plus signs in the file would be preceded and followed by a one-second interval in which no characters are transmitted.

To make the modem interpret the characters you type as the escape sequence, follow these steps:

1.	Before you type the escape sequence, send no characters to the modem for the length of time set up as the guard time.

2.	Type the escape sequence (+++), making sure to type the characters within the guard time.  Don't press <Enter> afterwards.

3.	Before transmitting more characters, wait for the length of time specified as the guard time.  When that time expires, the modem should display with the message "OK" on your screen.  The message indicates that the modem is in command mode.


AT command

Every modem command (except the A/ command and the escape sequence [+++]) must begin with the characters AT or at.  These characters are called the attention code.  The attention code tells the modem that modem commands follow.

Both of the attention code characters must be uppercase or lowercase characters.  The modem will not interpret the characters At or aT as attention codes.

____________
See also

Example of an AT command line

Steps for entering AT commands

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


A/ command

Repeats the last command line.

The modem stores the last command line in its command buffer until you enter a new command line and press <Enter>.  You can repeat the last command without retyping it by using this command:

A/

	NOTE:  This command doesn't begin with the AT attention code and doesn't need <Enter> at the end.


O command

Returns the modem to online mode.

If you've established a connection and the modem is in command mode, the O command returns your modem to online mode.  There are two ways for the modem to be in command mode when you have established a connection:

•	After you entered an escape sequence (+++).

•	After an on-to-off transition of the DTR signal, if you previously entered the &D1 command.

Format:  AT O<n>

The n parameter determines the option for returning to online mode:

ATO, ATO0	Returns the modem to online mode.

ATO1	Returns the modem to online mode and initiates a retrain sequence (2400 bps only).

A retrain sequence causes the connected modems to test the phone line characteristics and optimize their operation to get the best data transmission.

Training normally occurs when the modem initially establishes the connection.  If the line characteristics change during a session (possibly causing the data to become garbled), you can improve the connection without redialing by issuing the escape sequence to return to command mode and then issuing the ATO1 command to retrain the modems.

ATO2	Causes the modem to return to online mode and retrain for a lower line speed.

ATO3	Causes the modem to return to online mode and retrain for a higher line speed.


Commands that control result codes

These commands control which result codes the modem returns and their form:

Q<n>	Enables or disables result codes

V<n>	Displays numeric or verbal result codes

X<n>	Enables extended result codes and dialing options

\V<n>	Controls the inclusion of error control and data compression information with result codes


Q command

Enables or disables the display of result codes.

Format:  AT Q<n>

The n parameter controls the display of result codes:

ATQ, ATQ0	Tells the computer to display result codes in response to modem commands (factory setting).

ATQ1	Prevents the modem from sending result codes to your computer.  This disables only the result codes listed in the alphabetic list of result codes.  Even if you turn off the result codes, the modem displays S-register values, identification codes, checksum results, and results of diagnostics.


V command

Selects verbal or numeric result codes.

Format:  AT V<n>

The n parameter controls the display of verbal and numeric result codes:

ATV, ATV0	Display result codes as numbers.

ATV1	Display result codes as words (factory setting).

The alphabetical table of result codes lists verbal and numeric equivalents.  Numeric result codes are often useful when programs (rather than people) issue modem commands.


X command

Determines which result codes are enabled, and governs how the modem deals with dial tones and busy signals when dialing a phone number.

Format:  AT X<n>

The n parameter controls which result codes are enabled and lets you select dialing options:

ATX, ATX0	The modem returns only result codes 0 through 4.  See also the Table of Numeric Result Codes.

When dialing, the modem picks up the phone, waits for the amount of time specified in the S6 register (the factory setting is two seconds), and dials the number regardless of whether a dial tone is present.

When the modem establishes a connection, it displays a CONNECT result code.  If it can't establish a connection in the time specified in the S7 register (the factory setting is 30 seconds), it displays the NO CARRIER result code.

With this option, the modem doesn't recognize dial tones or busy signals.

ATX1	The modem returns result codes 0 through 5 and 9 through 20.  The modem's method of dialing is the same as for the X0 option.

With this option, the modem doesn't recognize dial tones or busy signals.

ATX2	The modem returns result codes 0 through 6 and 9 through 20.  The modem waits for a dial tone before dialing.  If a dial tone isn't received in five seconds, the modem displays a NO DIALTONE result code.

With this option, the modem doesn't recognize busy signals.

ATX3	The modem returns result codes 0 through 5, 7, and 9 through 20.  The modem's method of dialing is the same as for the X0 option, except that it recognizes a busy signal and displays the BUSY result code if it detects one.

After dialing, the modem expects a ringback signal within the time specified in the S7 register (the factory setting is 30 seconds).  After receiving the ringback, the modem waits up to one S7 time period for a carrier.  If either a ringback signal or a carrier does not occur, the modem displays the NO CARRIER result code.

With this option, the modem doesn't recognize dial tones.

ATX4	The modem returns result codes 0 through 7 and 9 through 20.  The modem waits for a dial tone before dialing.  If the modem doesn't receive a dial tone in five seconds, it displays a NO DIALTONE result code.  The modem displays a BUSY result code if it detects a busy signal.  The modem expects ringback and carrier signals as described in the X3 option.

With this option, the modem recognizes both dial tones and busy signals (factory setting).

Result codes 22 through 70 deal with error control and are controlled by the \V command, not the X command.

These result codes can't be disabled:

0	OK

1	CONNECT

2	RING

3	NO CARRIER

4	ERROR

These result codes can be disabled:

5	CONNECT 1200

6	NO DIALTONE

7	BUSY

8	NO ANSWER

9	CONNECT 300

10	CONNECT 2400

The following table summarizes the result codes returned for each setting of n:

SETTING FOR X<n>

_____________________________________________________________

RESULT CODES	X0	X1	X2	X3	X4
BUSY (7)				*	*
CONNECT (1)	*	*	*	*	*
CONNECT 300 (9)		*	*	*	*
CONNECT 1200 (5)		*	*	*	*
CONNECT 2400 (10)		*	*	*	*
ERROR (4)	*	*	*	*	*
NO ANSWER (8)
O CARRIER (3)	*	*	*	*	*
NO DIALTONE (6)			*		*
OK (0)	*	*	*	*	*
RING (2)	*	*	*	*	*
DIALING FUNCTIONS
Recognizes dial tone			*		*
Recognizes busy signal				*	*


\V command

Enables or disables the display of error control and data compression information.

The \V command works with the V command to display CONNECT result codes with error control and data compression information.  Specifically, the V command determines whether result codes are numeric or verbal, and the \V command determines whether reliable-connection (MNP or LAPM) information is included.

Format:  AT \V<n>

The n parameter specifies which result codes the modem returns:

AT\V0	Disables return of error control information with CONNECT result codes.  The modem returns only the result codes controlled by the X command (codes 0 through 20).  See the Table of Numeric Result Codes.

AT\V1	Returns minimal information with CONNECT result codes.  The result code tells whether the connection is reliable (uses error control), but it doesn't tell the type of error control or whether data compression is also used.  This command enables result codes 22 through 30.

Example:	A reliable connection at 2400 bps returns the following result code, regardless of the type of error control or data compression:

CONNECT 2400/REL

AT\V2	Returns full error control and data compression information with CONNECT result codes.  It tells the type of error control and whether data compression is used.  This command enables result codes 32 through 70 (factory setting).

Example:	A reliable connection at 2400 bps using LAPM error control and V.42bis data compression returns this result code:

CONNECT 2400/REL-LAPM-COMP

Example:	A reliable connection at 1200 bps using MNP error control without data compression returns this result code:

CONNECT 1200/REL-MNP

The CONNECT result codes for connections without error control aren't controlled by the \V command.  The X command has more information.

Example:	A reliable connection at 2400 bps using LAPM error control and V.42bis data compression returns this numeric result code:

64

____________
See also

Alphabetical table of result codes

Table of numeric result codes


Result codes

When you enter most modem commands, the modem displays a message on your screen indicating the results of the command.  These messages are called result codes.

Result codes are ASCII characters preceded and followed by a carriage return and line feed.  Result codes are returned in either verbal (words that describe the conditions) or numeric format.  The V command switches between verbal and numeric result codes.  You can also use the Q, X, and \V commands to determine which result codes the modem returns and how it presents them.

Choose one of these links to see:

Result codes in alphabetical order, with descriptions

Result codes in numeric order

Commands that control result codes


Result codes in alphabetical order

_____________________________________________________________________________________
VERBAL	NUMERIC	MODEM ACTION

BUSY	7	Busy signal detected.

CONNECT	1	With X0 option selected, connection established.  With X1
through X4 selected, connection established at 300 bits
per second (bps).

CONNECT 300/REL	22	The modem established a reliable (MNP)
connection at 300 bps.  (To receive this result code, the
\V1 command must have been entered.)

CONNECT 300/REL-MNP	32	The modem established a connection at 300 bps using
MNP error control.

CONNECT 1200	5	The modem established a connection at 1200 bps.

CONNECT 1200/REL	24	Connection established at 1200 bps using error control.

CONNECT 1200/REL-LAPM	54	The modem established a connection at 1200 bps using
LAPM error control.

CONNECT 1200/	64	The modem established a connection at 1200 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 1200/REL-MNP	34	The modem established a connection at 1200 bps using
MNP error control.

CONNECT 1200/	44	The modem established a connection at 1200 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 2400	10	The modem established a connection at 2400 bps.

CONNECT 2400/REL	25	The modem established a connection at 2400 bps using error control.

CONNECT 2400/REL-LAPM	55	The modem established a connection at 2400 bps using
LAPM error control.

CONNECT 2400/	65	The modem established a connection at 2400 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 2400/REL-MNP	35	The modem established a connection at 2400 bps using
MNP error control.

CONNECT 2400/	45	The modem established a connection at 2400 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 4800	11	The modem established a connection at 4800 bps.

CONNECT 4800/REL	26	The modem established a connection at 4800 bps
using error control.

CONNECT 4800/REL-LAPM	56	The modem established a connection at 4800 bps
using LAPM error control.

CONNECT 4800/	66	The modem established a connection at 4800 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 4800/REL-MNP	36	The modem established a connection at 4800 bps using
MNP error control.

CONNECT 4800/	46	The modem established a connection at 4800 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 7200	15	The modem established a connection at 7200 bps.

CONNECT 7200/REL	27	The modem established a connection at 7200 bps using
error control.

CONNECT 7200/REL-LAPM	57	The modem established a connection at 7200 bps using
LAPM error control.

CONNECT 7200/	67	The modem established a connection at 7200 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 7200/REL-MNP	37	The modem established a connection at 7200 bps using
MNP error control.

CONNECT 7200/	47	The modem established a connection at 7200 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 9600	12	The modem established a connection at 9600 bps.

CONNECT 9600/REL	28	The modem established a connection at 9600 bps using
error control.

CONNECT 9600/REL-LAPM	58	The modem established a connection at 9600 bps using
LAPM error control.

CONNECT 9600/	68	The modem established a connection at 9600 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 9600/REL-MNP	38	The modem established a connection at 9600 bps using
MNP error control.

CONNECT 9600/	48	The modem established a connection at 9600 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 12000	16	The modem established a connection at 12000 bps.

CONNECT 12000/REL	29	The modem established a connection at 12000 bps using
error control.

CONNECT 12000/REL-LAPM	59	The modem established a connection at 12000 bps using
LAPM error control.

CONNECT 12000/	69	The modem established a connection at 12000 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 12000/REL-MNP	39	The modem established a connection at 12000 bps using
MNP error control.

CONNECT 12000/	49	The modem established a connection at 12000 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 14400	17	The modem established a connection at 14400 bps.

CONNECT 14400/REL	30	The modem established a connection at 14400 bps using
error control.

CONNECT 14400/REL-LAPM	60	The modem established a connection at 14400 bps using
LAPM error control.

CONNECT 14400/	70	The modem established a connection at 14400 bps using
REL-LAPM-COMP	LAPM error control and data compression.

CONNECT 14400/REL-MNP	40	The modem established a connection at 14400 bps using
MNP error control.

CONNECT 14400/	50	The modem established a connection at 14400 bps using
REL-MNP-COMP	MNP error control and data compression.

CONNECT 19200	18	The modem established a connection with a
DTE speed of 19200 bps.

CONNECT 38400	19	The modem established a connection with a
DTE speed of 38400 bps.

CONNECT 57600	20	The modem established a connection with a
DTE speed of 57600 bps.

ERROR	4	There was an error in the command line, the command
line was too long, or the checksum returned by the
I command was incorrect.

NO ANSWER	8	You entered the @ (wait for quiet) dial modifier and the
modem didn't detect five seconds of silence within the
time-out period specified in the S7 register (the factory
setting is 30 seconds).

NO CARRIER	3	The modem lost the carrier or never received it within the
time-out period specified in the S7 register (the factory
setting is 30 seconds).

NO DIALTONE	6	The modem didn't receive a dial tone within the specified
time period.  If you entered the W dial
modifier,
the subsequent dial tone must be detected
within the time specified in the
S7 register
(the factory setting is 30 seconds).  If you
entered the X2 or
X4 command, the dial tone must occur
within five seconds after the modem picks up the phone.

OK	0	Command accepted; no errors occurred.

RING	2	The local phone line is ringing, indicating an incoming call.


Result codes in numeric order

NUMERIC	VERBAL CODE
CODE

0	OK

1	CONNECT

2	RING

3	NO CARRIER

4	ERROR

5	CONNECT 1200

6	NO DIALTONE

7	BUSY

8	NO ANSWER

10	CONNECT 2400

11	CONNECT 4800

12	CONNECT 9600

15	CONNECT 7200

16	CONNECT 12000

17	CONNECT 14400

18	CONNECT 19200

19	CONNECT 38400

20	CONNECT 57600

24	CONNECT 1200/REL

25	CONNECT 2400/REL

26	CONNECT 4800/REL

27	CONNECT 7200/REL

28	CONNECT 9600/REL

29	CONNECT 12000/REL

30	CONNECT 14400/REL

32	CONNECT 300/REL-MNP

34	CONNECT 1200/REL-MNP

35	CONNECT 2400/REL-MNP

36	CONNECT 4800/REL-MNP

37	CONNECT 7200/REL-MNP

38	CONNECT 9600/REL-MNP

39	CONNECT 12000/REL-MNP

40	CONNECT 14400/REL-MNP

44	CONNECT 1200/REL-MNP-COMP

45	CONNECT 2400/REL-MNP-COMP

46	CONNECT 4800/REL-MNP-COMP

47	CONNECT 7200/REL-MNP-COMP

48	CONNECT 9600/REL-MNP-COMP

49	CONNECT 12000/REL-MNP-COMP

50	CONNECT 14400/REL-MNP-COMP

54	CONNECT 1200/REL-LAPM

55	CONNECT 2400/REL-LAPM

56	CONNECT 4800/REL-LAPM

57	CONNECT 7200/REL-LAPM

58	CONNECT 9600/REL-LAPM

59	CONNECT 12000/REL-LAPM

60	CONNECT 14400/REL-LAPM

64	CONNECT 1200/REL-LAPM-COMP

65	CONNECT 2400/REL-LAPM-COMP

66	CONNECT 4800/REL-LAPM-COMP

67	CONNECT 7200/REL-LAPM-COMP

68	CONNECT 9600/REL-LAPM-COMP

69	CONNECT 12000/REL-LAPM-COMP

70	CONNECT 14400/REL-LAPM-COMP


Alphabetical list of AT commands

The following table lists the modem commands in alphabetical order, with a brief description of each command's function.  Defaults are followed by an asterisk.

COMMAND	DESCRIPTION

+++	Escape sequence, returns to command mode

A	Answers manually

A/	Repeats the last command line

AT	Attention code:  Must precede all commands but A/ and +++

B<n>	Sets handshake mode (0=CCITT, 1=Bell*)

D <string>	Dial phone number <string>, with modifiers (tone=default)

E<n>	Sets echo mode in command mode (0=off, 1=on*)

H<n>	Switch hook control (0=on hook, 1=off hook)

I<n>	Returns product code and checksum

L<n>	Controls speaker volume (1=low volume*)

M<n>	Determines when speaker is on or off (default=1, on until carrier detected)

O<n>	Sets conditions to return to online mode

Q<n>	Enables (0*) or disables (1) result codes

S<r>	S Register read/write commands

V<n>	Numeric (0) or verbal (1*) result codes

X<n>	Enables extended result codes and dialing options

Y<n>	Long space disconnect (0=disabled*, 1=enabled)

Z<n>	Resets to configuration n

&C<n>	Data carrier detect (DCD) options

&D<n>	Data terminal ready (DTR) signal control options

&F<n>	Fetches factory configuration profile

&G<n>	Sets guard tone mode (0=off*)

&H<n>	Displays help list of AT command descriptions

&P<n>	Sets make-to-break pulse dial ratio (0=US*)

&S<n>	Data set ready (DSR) options (0=always on)

&T<n>	Controls diagnostic test commands in Direct Mode

&V	View active configuration profile

&W<n>	Writes active configuration profile <n> to nonvolatile memory

&Y<n>	Recalls profile <n> when modem is powered up

&Z<n>=<x>	Stores telephone number x in location n

\A<n>	Sets maximum MNP block size (256 bytes*)

\B<n>	Transmit break time (fixed at \B3, 300 ms)

\C<n>	Sets auto-reliable buffer (0=disabled*)

\G<n>	Sets modem-to-modem XON/XOFF (software) flow control (0=disabled*)

\J<n>	Serial data (BPS) rate adjustment (0=disabled*, 1=enabled)

\K<n>	Sets MNPbreak control

\N<n>	Sets operating mode (default=auto-reliable LAPM/MNP mode)

\O	Originates reliable MNP connection

\Q<n>	Sets serial port flow control (default=bidirectional CTS/RTS)

\T<n>	Sets inactivity timer (n=0* to 90 seconds)

\U	Accepts reliable MNP connection

\V<n>	Controls the inclusion of error control and data compression information with result codes

\X<n>	Sets XON/XOFF pass-through to remote modem

\Y	Switches to reliable mode

\Z	Switches to normal mode

"H<n>	Enables or disables V.42bis data compression (default=enabled bidirectionally)

%A<n>	Sets auto-reliable fallback character

%C<n>	Sets data compression (0=off, 1=on*)

%E<n>	Sets auto retrain (0=disabled, 1=enabled*)

+FCLASS=<n>	Specifies data modem or fax operating mode, and returns information about the current
selection

-J<n>	Controls V.42 error control detection phase


Making a call

For information on making a call, see these topics:

D <string>	Dial phone number <string>, with modifiers

H<n>	Switch hook control (0=on hook, 1=off hook)

&Z<n>=<x>	Stores telephone number x in location n

Manual dialing	Explains how to dial manually


D command

Directs the modem to dial a phone number.

Format:  AT D <string>

The string parameter is a series of characters that can include a phone number and one or more dial modifiers that give the modem additional instructions on how to place the call.  The length of the string is limited to the amount of space in the command buffer (40 characters plus the AT command prefix and the <Enter> that ends the command).

The characters you can include in the phone number depend on whether you use pulse or tone dialing:

•	Pulse dialing, normally used in rotary phones, uses a series of pulses to indicate a phone number (one pulse for a one, two pulses for a two, and so on).  With pulse dialing, the phone number can contain the numbers 0 through 9.  (The modem ignores the characters A, B, C, D, #, and * if you choose pulse dialing.)

•	Tone dialing, normally used in push-button phones, uses tones of different frequencies to represent different numbers.  With tone dialing, the phone number can contain the numbers 0 through 9 plus the characters A, B, C, D, #, and *.

The modem ignores any characters in the <string> parameter other than the phone number and dial modifiers.  This lets you include spaces and punctuation characters (such as hyphens and parentheses) to make phone numbers more readable, without affecting the number you're dialing.  However, even though the modem ignores the extra characters, all characters except space characters take up space in the command buffer.

Example	The following command dials a number without including any dial modifiers or punctuation:

ATD15035559999

Example	The following command dials the same number, but includes spaces and punctuation to make the command easier to read:

AT D 1 (503) 555-9999

Example	The following command dials the same number, but includes a dial modifier to specify tone dialing:

AT DT 1-503-555-9999

Tone dialing has been preset in your configuration profile.  This preset value remains in effect until you give the AT&F&W command.  If you want to restore factory defaults but still keep this preset value, use the ATZ command instead of AT&F.  If you accidentally overwrite this preset value, you can set up tone dialing as the default using the AT&W command.  See information on configuration commands.

You can include multiple modem commands on one command line.  However, if you include the D command on the same line with other modem commands, the D command (plus any phone number and dial modifiers) must be the last command on the line.  If you place other commands after the D command, the modem treats them as if they were punctuation characters in the D command's parameter string and ignores them.

Example	The H command tells the modem to hang up the phone.  To include both the H and D commands in a single line, the H command must come before the D command, as in this command line:

AT H D 1-503-555-9999

In the following command line, the H command is ignored because the modem considers it part of the D command's parameter string:

AT D  1-503-555-9999 H

After you enter the D command, the modem goes off-hook (which is the same as picking up the receiver) and waits for a dial tone.  The length of time it waits depends on the setting of the X command and the contents of the S6 register.

After the time expires, the modem dials the phone number and waits for a carrier signal from the remote modem.  The length of time the modem waits for a carrier is set at the factory to 30 seconds; you can reset it by changing the S7 register.

If the modem doesn't receive a carrier signal within the time-out interval, it hangs up the phone and displays the NO CARRIER message.

If the modem receives a carrier signal, it displays one of the CONNECT result codes.  Which result code it returns depends on the communication rate and the settings of the X and \V commands.


Dial modifiers

These are the dial modifiers; choose the link for detailed information:

P	Pulse dialing

R	Reverse mode

S	Dial a stored number

T	Tone dialing (factory setting)

W	Wait for a subsequent dial tone

@	Wait for quiet

, (comma)	Pause before sending the next character

; (semi-colon)	Place modem in command mode after dialing

! (exclamation)	Hook flash


P -- Pulse dial modifier

The P command tells the modem to use pulse dialing when it dials the phone.  You can switch between pulse and tone dialing by using the P and T dial modifiers.  Once you indicate a method of dialing, that method remains in effect until you specify another method or turn off the power -- unless you save it with the &W command.

You can use the P command as a dial modifier for the D command, or you can enter it as a command by itself without dialing a phone number.

Example	The following command dials a number using pulse dialing.  The P command is used as a dial modifier.

AT DP 1 (503) 555-9999

Example	The following two commands are equivalent to the command in the previous example.  The first command sets pulse dialing.  The second command dials the number using pulse dialing.

ATP

AT D 1 (503) 555-9999


R-- Reverse dial modifier

When you dial the phone with the D command, your modem changes to originate mode.  The R dial modifier originates a call in reverse.  That is, after your modem connects to the remote modem, your modem switches to answer mode.  This lets it communicate with originate-only modems.

The R dial modifier must be the last character in the line containing the D command.

Example	The following command dials a phone number and places the modem in answer mode:

AT D 1-503-555-9999 R


S -- Dial stored phone number

The S dial modifier tells the modem to dial a phone number stored in the modem's nonvolatile RAM (NVRAM).  You can store a phone number in NVRAM by using the &Z command.

Example	The following command dials the number stored in NVRAM at location n:

AT DS=n

The n parameter specifies the location of a telephone number in NVRAM.  Valid values are 0,1,2, and 3.


T -- Tone dial modifier

The T command tells the modem to use tone dialing when it dials the phone.  Tone dialing is the factory dialing method.  Once you specify the T command, tone dialing remains in effect until you specify pulse dialing (with the P command) or turn off the modem--unless you save it with the &W command.

You can use the T command as a dial modifier for the D command, or you can enter it as a command by itself without dialing the phone.

Example	The following command dials a number using touch tone dialing.  The T command is used as a dial modifier.

AT DT 1 (503) 555-9999

Example	The following two commands are equivalent to the command in the previous example.  The first command sets tone dialing.  The second command dials the number.

ATT

AT D 1 (503) 555-9999

Example	The following command combines pulse and tone dialing in one command, dialing 9 using pulse dialing and dialing the rest of the number using tone dialing:

AT DP 9 T 1 503 555 9999


W -- Wait for a subsequent dial tone

The W dial modifier tells the modem to wait for another dial tone before dialing the numbers that follow the W.  The W dial modifier affects a subsequent dial tone only (such as dialing 9 for an outside line and waiting for another tone).  This dial modifier doesn't affect the time the modem waits for the first dial tone, which you set with the X command.

The length of time the modem waits is set at the factory to 30 seconds.  You can change this value by modifying the S7 register.  Be careful when you change the S7 register, because the value of the S7 register is also the time to wait for a carrier to be detected.

Example	The following command dials an access code (9) and then waits up to 30 seconds for a dial tone before continuing to dial the remaining numbers:

AT DT 9 W 1 (503) 555 9999


@ -- Wait for quiet

The @ dial modifier tells the modem to wait a specified time for five seconds of silence.  Once the modem detects five seconds of silence, it continues dialing the numbers that follow the @.  The default is 30 seconds.  You can change this value by modifying the S7 register register.

Example	The following command dials an access code (9) and then waits for the time interval specified in S7 for five seconds of silence before continuing to dial the remaining numbers:

AT DT 9 @ 1 (503) 555 9999


, -- Pause dial modifier

The , (comma) dial modifier tells the modem to pause while dialing.  This is useful when you're calling from PBX systems that require dialing a number, such as 9, to get an outside line.  With these systems, you usually can't continue dialing until you receive another dial tone.  The comma lets you wait before continuing to dial, giving the phone system enough time to respond with a dial tone.

The default pause time is 2 seconds.  To change this value, modify the S8 register.  You can also include multiple commas in the D command to extend the length of time the modem waits.

Example	The following command uses tone dialing to dial a number.  It pauses for four seconds between the access code (9) and the rest of the number.

AT DT 9,,1 (503) 555-9999


; -- Place modem in command mode after dialing

The ; (semicolon) dial modifier returns the modem to command mode after dialing a number.  It doesn't connect to the remote modem, but it holds the line for further commands.  When the modem finishes dialing the number, it displays OK.

Put the semicolon dial modifier at the end of the command line.

The semicolon dial modifier is especially useful when you need to dial a sequence of numbers that's too long to fit in one command line; that is, one that causes the D command to be longer than 40 characters.  By using the semicolon dial modifier, you can break the long number into two commands.  The semicolon is also helpful in electronic transactions (such as banking by phone) to transmit codes and amounts without causing the modem to connect to the remote source in data mode.

Entering the ATO command after returning to command mode tells the modem to begin the handshake process.

Example	The following two commands dial a single phone number.  The semicolon dial modifier at the end of the first command tells the modem to return to command mode without releasing the line.  The second command dials the remaining numbers and connects to the remote modem.

AT DT 1 503 555;

OK  (modem response)

AT DT 9999


\! -- Hook flash dial modifier
! -- Hook flash dial modifier

The ! dial modifier tells the modem to go on-hook (hang up) for 1/2 second.  This modifier is useful in PBX systems, where you can use a hook flash to access other phone services, such as transferring a call.


H command

Switch hook control

Use the H command to control the phone line relay.  The most common use for this command is to hang up the phone from command mode.

Format:  AT H<n>

The n parameter governs how the phone line relay is controlled:

ATH, ATH0	Causes the line relay to go on-hook (hangs up the phone).

ATH1	Causes the line relay to go off-hook (equivalent to picking up the phone), but does not dial or handshake.  Use H1 only for testing and evaluation.

Example	This command hangs up the phone:

ATH


&Z command

Stores a phone number and its dial modifiers in the modem's nonvolatile RAM (NVRAM).  NVRAM maintains the stored number even when you turn off your computer.

Format:  AT &Z<n>=<string>

The n parameter specifies a location in NVRAM where the number will be stored.  Internal modems can store only one phone number, so n always equals 0.

The string parameter is similar to the D command's string parameter.  It is a series of characters that includes the phone number and any dial modifiers you want to be in effect when dialing the number.

•	Pulse dialing:  The phone number can use the digits 0 through 9.

•	Tone dialing:  The phone number can use the digits 0 through 9 plus the characters A, B, C, D, #, and *.

•	Dial modifiers:  Includes the characters P, T, R, W, , (comma), !, @, and ; (semicolon).  (You can't use the S dial modifier or the / dial modifier with the &Z command.)

The string parameter can have up to 36 characters.  Characters other than those listed above are ignored and not included in the count.  If you enter more than 36 characters, the modem displays the ERROR message and stores no characters.

To dial a number stored in NVRAM with the &Z command, use the DS command.

Example	This command stores the tone-dialed number (9-1-503-555-9999) in location 0:

AT&Z0=T9,,1-503-555-9999

This command dials the number just stored:

AT DS=0


Answering a call

There are two options for answering a call:

Manual answering, using the A command

Modem auto-answer, controlled by the S0 register


A command

Tells the modem to go off-hook (to pick up the phone) immediately, whether or not the telephone is ringing, and to take control of the telephone line in answer mode.

Format:  AT A

When manually answering a call from a remote modem, you normally wait until your telephone rings, causing your modem to display the RING result code on your screen.  You can then enter the A command to answer the telephone and connect with the remote modem.

After you enter the A command and the modem answers the phone, the modem is in online mode.  In this mode, the modem doesn't accept modem commands from you.  You can return the modem to command mode by typing the escape sequence (+++).


Modem auto-answer

To set up the modem to answer automatically, set the S0 register to a nonzero value.

Format to set the S0 register:  AT S0=<n>

The n parameter indicates whether the modem answers.  If n is set to 0, the modem won't answer.  If n is set to 1-255,  the modem will answer on the number of rings specified in your communications software.

Even if you set the modem to automatically answer the phone, you can still use the A command to override the automatic answer facility and manually answer the phone.


Communication option commands

These commands control the way the modem communicates:

B<n>	Sets handshake mode (0=CCITT, 1=Bell*)

E<n>	Sets echo mode in command mode (0=off, 1=on*)

L<n>	Controls speaker (0=off, 1-3=on)

M<n>	Determines when speaker is on or off

Y<n>	Long space disconnect (0=disabled*, 1=enabled)

&C<n>	Data carrier detect (DCD) options

&D<n>	Data terminal ready (DTR) signal control options

&G<n>	Sets guard tone mode

&P<n>	Sets make-to-break pulse dial ratio

&S<n>	Data set ready (DSR) options (0=always on)

%E<n>	Sets auto retrain (0=disabled, 1=enabled*)

+FCLASS	Specifies data modem or fax operating mode, and returns information about the current selection.


B command

Selects the modulation protocol.

Format:  AT B<n>

The n parameter lets you choose between CCITT and Bell standards, when operating at various modem rates:

When you enter the B command:

ATB, ATB0	Sets the modem to the following CCITT standards at these modem rates:

300 bps	V.21

1200 bps	V.22

2400 bps 	V.22bis/V.22/Bell 212A

9600 bps	V.32bis/V.32/V.22bis/V.22/V.21

ATB1	Sets the modem to the following Bell standards at these modem rates (factory setting):

300 bps	Bell 103

1200 bps	Bell 212A (also Bell 103 answer mode)

2400 bps	V.22bis/V.22/Bell 212A

9600 bps	V.32bis/V.32/V.22bis/V.22/Bell 212A

ATB2	Sets the modem to the following standards: V.32bis/V.32/V.22bis/V.22/V.21/Bell 212A

ATB4	Sets the modem to the Bell 103 standard.

ATB5	Sets the modem to the V.22/Bell 212A standards.

ATB6	Sets the modem to the V.22bis standard.

ATB7	Sets the modem to the V.32 standard at 4800 bps.

ATB8	Sets the modem to the V.32 standard at 9600 bps.

ATB9	Sets the modem to the V.32bis standard.


E command

Determines whether the modem echoes (sends) the commands you enter to your computer screen as you type them.

Format:  AT E<n>

The n parameter sets the echo mode:

ATE, ATE0	Sets the modem to not echo local commands.  This means you won't see modem commands as you type them.

ATE1	Sets the modem to echo local commands (factory setting).


L command

Controls the speaker volume.  (Use the M command to turn the speaker on and off.)

Format:  AT L<n>

The n parameter selects the volume level.

ATL, ATL0, or ATL1  Selects low volume (factory setting).

ATL2                Selects medium volume.

ATL3                Selects high volume.


M command

Turns the speaker on or off.

Format:  AT M<n>

The settings for the n parameter are:

ATM, ATM0	Turns off the speaker at all times.

ATM1	Turns the speaker on until the modem receives a carrier signal from the remote modem, or until a V.32 or V.32bis retraining sequence begins.  This setting lets you monitor both the dialing and carrier-handshaking progress (factory setting).

ATM2	Turns the speaker on at all times.

ATM3	Turns the speaker on until the modem receives a carrier signal from the remote modem, but off while the modem dials.  This setting lets you monitor the carrier handshaking progress.


Y command

Controls whether the modem disconnects when it receives a break signal of 1.6 seconds or longer from the remote modem.

Format:  AT Y<n>

The n parameter determines the setting:

ATY, ATY0	Disables the long space disconnect feature.  Receiving a break signal won't cause the modem to disconnect (factory setting).

ATY1	Sets the modem to disconnect when it receives a break signal of 1.6 seconds or longer from the remote modem.  When the modem receives an H0 command to disconnect, it sends a 4-second break signal before disconnecting.  It also sends a break signal if you've invoked the &D2 command and an on-to-off transition of the DTR signal occurs.


&C command

Controls how the modem treats the data carrier detect (DCD) signal.

The DCD signal indicates whether the modem is receiving a carrier from a remote modem.  This setting depends on the communication software you are using with the modem.  Most communications software uses the factory value (&C1).

Format:  AT &C<n>

The n parameter determines how DCD is treated:

AT&C, AT&C0	The DCD signal is always on.

AT&C1	The DCD signal matches the state of the remote modem's data carrier.  That is, when the modem is receiving a suitable data carrier, DCD is on (factory setting).


&D command

Controls how the modem treats the data terminal ready (DTR) signal.

The DTR signal indicates whether a local computer is connected to a local modem.  The setting of this option depends on the communications program you're using with the modem.  Most communications programs use the factory setting (&D2).  Applications such as bulletin board software, programs that control multiple phone lines, or multitasking or multiuser applications might require other settings.

Format:  AT &D<n>

The n parameter determines how DTR is treated:

AT&D, AT&D0	The modem ignores the DTR signal.

AT&D1	The modem switches from data to command mode when DTR switches from on to off.

AT&D2	When DTR switches from on to off, the modem switches from data to command mode, goes on-hook (hangs up), and disables auto answer (factory setting).  You can re-establish auto answer by turning on DTR.

AT&D3	When DTR switches from on to off, the modem resets to a user-specified configuration, set with the &W command.

The &D command (&D1, &D2, and &D3) set up the modem to react to changes in DTR.  To have an effect, the new state of DTR must last longer than the time specified in the S25 register.


&G command

Controls the generation of guard tones in V.22 and V.22bis only.

These tones are used internationally, except in the United States, to indicate that a line is ready to receive data.

Format:  AT &G<n>

The n parameter determines the guard tone:

AT&G, AT&G0	No guard tones (factory setting).

AT&G1	The modem generates a 550-Hz guard tone.

AT&G2	The modem generates an 1800-Hz guard tone.


&P command

Controls the ratio of off-hook time (make) to on-hook time (break) during pulse dialing.  Set this ratio as required by the phone system of the country you're in.

Format:  AT &P<n>

The n parameter selects the make-to-break ratio:

AT&P, AT&P0	Sets a ratio of 39% make to 61% break at 10 pps, which is the standard for the United States and Canada (factory setting).

AT&P1	Sets a ratio of 33% make to 67% break at 10 pps, which is compatible with the United Kingdom and Hong Kong.


+FCLASS command

Specifies data or fax operating mode and returns information about the current selection.  While you're using the AT commands, the modem should be set to data mode.  (Your fax application software controls the change from data to fax mode.)  If the modem is accidentally placed in fax mode, use this command to return it to data mode.

Format:  AT +FCLASS=<n>

The forms of this command are:

+FCLASS=0	Puts the modem in data modem mode (factory setting).

+FCLASS?	Displays your modem's current service class (0=data modem)

+FCLASS=?	Displays your modem's service class capabilities (0=data modem capabilities, 2=faxmodem, class 2)


Error control and data compression commands

This section provides the following information and command descriptions (* = default):

Error control protocols

\A<n>	Sets maximum MNP block size

\B<n>	Transmit break (fixed at \B3, 300 ms)

\C<n>	Sets auto-reliable buffer

\G<n>	Sets modem-to-modem XON/XOFF (software) flow control

\J<n>	Serial data (BPS) rate adjustment (0=disabled*, 1=enabled)

\K<n>	Sets break control

\N<n>	Sets operating mode

\O	Originates reliable MNP connection

\Q<n>	Sets serial port flow control

\T<n>	Sets inactivity timer (n=0* to 90 seconds)

\U	Accepts reliable MNP connection

\X<n>	Sets XON/XOFF pass-through to remote modem

\Y	Switches to reliable mode

\Z	Switches to normal mode

%A<n>	Sets auto-reliable fallback character

%C<n>	Sets data compression (0=off, 1=on*)

-J<n>	Controls V.42 detection phase

"H<n>	Enables or disables V.42bis data compression


Error control protocols

Your modem supports two error control protocols that compensate for noisy phone lines and other signal distortions that can introduce errors into the data you send with your modem.  Both protocols detect errors and resend blocks of data until all the data has been sent error-free.  The protocols are:

•	Link Access Procedure for Modems (LAPM) -- recommended in the CCITT V.42 specification as the primary error control protocol.

•	Microcom Networking Protocol (MNP) -- recommended in the CCITT V.42 specification as the backup error control protocol.

Establishing the error control protocol

When your modem dials a remote modem, it automatically negotiates to set up the error control protocol that both modems support.  It tries to establish a connection in this order:

•	LAPM can work with the data compression protocol that conforms to the CCITT V.42bis specification for data compression.  When your modem is communicating with another modem that supports V.42bis data compression, they can communicate up to four times faster than if they were transmitting data without using data compression.

•	MNP error control classes 1-4 can use the MNP class 5 data compression protocol.  When your modem is communicating with another modem that supports MNP class 5 data compression, they can communicate up to two times faster than they can without using data compression.

These terms describe the different types of connections that result:

•	Normal connection:  doesn't use an error correction protocol.

•	Reliable connection:  uses error control (either LAPM or MNP).

•	V.42 connection:  modems can negotiate between LAPM and MNP, but must use one of the two.

•	Auto-reliable connection:  modems are free to negotiate among LAPM, MNP, and normal connections.

To change the way your modem negotiates setting up an error control protocol, use the \N command.


\A command

Specifies the maximum size for a data block during MNP class 4 and 5 operations.

Format:  AT \A<n>

The n parameter sets the maximum block size:

AT\A, AT\A0	Sets the maximum block size to 64 bytes.

AT\A1	Sets the maximum block size to 128 bytes.

AT\A2	Sets the maximum block size to 192 bytes.

AT\A3	Sets the maximum block size to 256 bytes (factory setting).

Sending large blocks of data when phone lines are noise-free improves performance by reducing error-control overhead.  Sending small blocks of data when phone lines are noisy improves performance by reducing retransmissions.

The \A command doesn't affect MNP class 3 or lower operations.


\B command

Sends a break signal to the remote modem.

Format:  AT \B<n>

The transmit break is fixed at \B3, 300 milliseconds.


\C command

Controls whether the local modem will buffer data coming from the remote modem while the two modems are negotiating for a reliable (LAPM or MNP) connection.  It also determines whether the modem will try to detect the fallback character specified with the %A command.

Format:  AT \C<n>

The n parameter determines whether the data received by the modem is buffered and how the fallback character is handled:

AT\C, AT\C0	While negotiating for a reliable connection, no buffering occurs, and fallback-character detection is disabled (factory setting).

AT\C1	The local modem buffers up to 200 characters on the answering modem while negotiating for a reliable connection, and no fallback-character detection occurs.  If the buffer fills with data, or if 4 seconds elapse from the time of connection before a reliable connection is made, the local modem makes a normal connection and passes the buffered data to the local computer.

AT\C2	No buffering of data occurs on the answering modem during negotiation for a reliable connection.  Fallback-character detection occurs.  If the modem detects the fallback character while it's trying to make a reliable connection, it makes a normal connection.


\G command

Turns on modem-to-modem XON/XOFF flow control (software flow control) during a normal mode connection.

XON/XOFF flow control helps the modem handle data more efficiently when it is receiving data from the remote modem faster than it can process the data.  See the \Q command and the \X command for more information on XON/XOFF flow control.

Format:  AT \G<n>

The n parameter turns XON/XOFF flow control on and off:

AT\G, AT\G0	Turns off XON/XOFF flow control (factory setting).

AT\G1	Turns on XON/XOFF flow control.  Because the modem-to-computer rate is usually greater than the modem-to-modem rate, the \G1 command is rarely used or needed.


\J command

Lets the modem adjust the rate at which it exchanges data with the computer through the communications port (baud rate), regardless of the modem-to-modem connection speed.

Format:  AT \J<n>

The n parameter enables or disables the serial data rate adjustment:

AT\J, AT\J0	Disables serial data rate adjustment.  This lets you maintain a high data rate between the computer and the modem, even when the modem is communicating with another modem at a lower data rate.  This option is especially useful with data compression (factory setting).

AT\J1	Enables data rate adjustment, so the serial data rate is automatically adjusted to match the modem-to-modem data rate.  Use this setting if your communication software is set up to recognize the modem's responses and switch to the correct baud rate.

If you use this option, make sure the \Q command is set to its factory setting.  Otherwise you may lose data.


\K command

Tells the modem how to handle a break signal received from either the local computer or the remote modem.

Format:  AT \K<n>

The n parameter determines how the modem handles a break signal.  The possible values for n depend on the following three possible conditions of the modem-to-modem connection.

1.	If the break is received from the local computer during reliable or normal connection:

\K0	Purge buffers, send break to local computer, no break sent to remote modem.

\K1	Purge buffers, immediately send break to remote modem.

\K2	Same as \K0.

\K3	Immediately send break to remote modem.

\K4	Same as \K0.

\K5	Send break to remote modem in sequence with data (factory setting).

2.	If the break is received from a remote modem during a normal connection:

\K0	Purge buffers, immediately send break to local computer.

\K1	Same as \K0.

\K2	Immediately send break to local computer.

\K3	Same as \K2.

\K4	Send break to local computer in sequence with data.

\K5	Same as \K4 (factory setting).

3.	If a \B<n> command is received from the local computer while in command mode during a reliable or normal connection:

\K0	Purge buffers, send break to remote modem.

\K1	Same as \K0.

\K2	Immediately send break to remote modem.

\K3	Same as \K2.

\K4	Send break to remote modem in sequence with data.

\K5	Same as \K4 (factory setting).


\L command

Sets MNP link type.

The MNP link type might need to be changed so that the protocol of the sending and receiving modems will match.

Format:  AT \L<n>

The n parameter controls the link type:

AT\L0	Stream (factory setting)

AT\L1	Block


\N command

Determines the type of asynchronous connection the modem will try.

Format:  AT \N<n>

The n parameter specifies the type of connection:

AT\N0	Forces a normal connection.

AT\N1	Direct operating mode for diagnostics.

AT\N2	Reliable MNP mode.

AT\N3	Auto-reliable LAPM/MNP mode (factory setting).

AT\N4	Reliable LAPM/MNP mode.

A modem that's only LAPM can't communicate with a modem using MNP.  This command guarantees that your modem will be able to automatically communicate with modems that support LAPM, MNP, or no error control.

The following table describes the types of connections you can make between an originating and answering modem, depending on how you set the \N command.  The modem's factory setting is \N3.  (The \N1 option isn't shown in this table because it's reserved.)

\N0, \N2, \N3, and \N4 modes use the hardware flow control method defined by the \Q command.

\N SETTINGS AND CONNECTION TYPES

	\N Setting for Originating Modem
\N Setting for Answering Modem	AT\N0	AT\N2	AT\N3	AT\N4
AT\N0	Normal	Modems hang up	Normal	Modems hang up
AT\N2	Modems hang up	MNP	MNP	MNP
AT\N3	Normal	MNP	LAPM	LAPM
AT\N4	Modems hang up	MNP	LAPM	LAPM


\O command

Lets you switch online to an MNP reliable connection after you've made a normal connection.

Format:  AT \O

You can use this command regardless of whether the local modem originated or answered the call.  Before you use this command, you must establish a normal connection with the remote modem, and the \U command must have been sent to the remote modem.  You then have 12 seconds to type the escape sequence +++ and enter the \O command.

The local modem tries to originate an MNP reliable connection as soon as it receives the \O command.  If the modem can't make a reliable connection, it tries again.  If the second try fails, the modem returns to its normal connection.  If the modem has already established an MNP reliable connection, the \O command won't change this connection.

____________
See also

\Y command


\Q command

Selects the type of flow control used between the local modem and the local computer to prevent the modem's buffer from overflowing.

You can choose from two types of flow control:

•	Software flow control (XON/XOFF--transmit-on/transmit-off), where the modem inserts ASCII characters in the data stream to control data flow.  XON/XOFF flow control is slower than CTS/RTS flow control because XON and XOFF are ASCII characters that must be transmitted with the rest of the data.

•	Hardware flow control (CTS/RTS--clear-to-send/request-to-send), where dedicated TIA-232 signal lines between the modem and the local computer are used to control data flow.  CTS/RTS flow control is very fast because CTS and RTS are TIA-232 signals.

Both types allow the modem to tell the local computer to:

•	Stop sending data to the modem when the modem's data buffer is full.

•	Start sending data again when the buffer can hold more data.

Format:  AT \Q<n>

The n parameter specifies the flow control method:

AT\Q, AT\Q0	Turns off all flow control.

AT\Q1	Selects bidirectional XON/XOFF (software) flow control.  The modem and local computer send ASCII characters to start and stop data transmission between the two.  (Also see the \G and the \X command.)

AT\Q2	Selects unidirectional CTS flow control.  The modem tells the local computer that the modem is ready for more data by turning on the CTS signal.  The modem turns off the CTS signal to tell the computer not to send data.

AT\Q3	Selects bidirectional CTS/RTS flow control.  The modem and local computer use the CTS signal to start and stop data transmission.  When the computer sends an RTS signal, the modem knows that the computer wants to transmit data.  If the modem is ready to receive the data, it replies with a CTS signal.  Likewise, the modem sends the computer a CTS signal when it has data to send to the computer, which sends an RTS signal when it can receive data (factory setting).


\T command

Tells the modem to disconnect if no data activity has occurred during the time specified.

Format:  AT \T<n>

The n parameter specifies the length of time to wait, where n is between 0 and 90 seconds.  The default is 0, which disables the inactivity timer.


\U command

Sets up the modem to accept an online request from the remote modem to switch to an MNP reliable connection, after you've already established a normal connection.

Format:  AT \U

You can use this command regardless of whether the local modem originated or answered the call.

Before you use this command, you must establish a normal connection with the remote modem.  You then type the escape sequence +++ (to go to command mode) and enter the \U command.

The local modem then waits 12 seconds for a request from the remote modem to establish the MNP reliable connection.  If the connection attempt fails, the modem returns to its normal connection.  If the modem has already made an MNP reliable connection, the \U command won't change this connection.

____________
See also

\O command

\Y command.


\X command

Controls whether the XON and XOFF characters are sent from the local modem to the remote modem.

When the \Q1 command is in effect, the host computer and local modem use XON and XOFF characters (software flow control) to control the flow of data between the computer and the local modem.  Also see the \G and the XON/XOFF glossary entry.

Format:  AT \X<n>

The n parameter specifies whether to pass the XON and XOFF characters to the remote modem:

AT\X, AT\X0	Recognize but don't pass the XON and XOFF characters to the remote modem (factory setting).

AT\X1	Recognize and pass the XON and XOFF characters to the remote modem.


\Y command

Switches to MNP reliable connection while online.

Format:  AT \Y

Before sending the \Y command, type the escape sequence +++ to enter command mode.

The \Y command combines the functions of the \O and \U commands, letting you switch online to an MNP reliable connection once you've already made a normal connection.

If the modem can't establish an MNP reliable connection, it returns to the normal connection.  If the modem has already established an MNP reliable connection, the \Y command won't change this connection.


\Z command

Switches from MNP to normal connection.

Format:  AT \Z

Before sending the \Z command, type the escape sequence +++ to enter command mode.

When the modem ends the MNP reliable connection and switches to a normal connection, any data in the buffers is lost.

If the modem is currently operating with a normal or LAPM connection, entering the \Z command won't change that connection.


%A command

Specifies the ASCII character that tells the modem to return (fallback) from reliable mode to normal mode when the \C2 command is in effect.

Format:  AT %A<n>

Default:  0 (null character)

You must enter the %A command before the reliable connection is made for the command to be effective.

The n parameter determines the fallback character and can be any decimal integer between 0 and 127.  The value of n represents the ASCII code for the keyboard character that you wish to use as the fallback character.  (If you enter the fallback character from the keyboard while the modem is negotiating for a reliable connection, the modem falls back to a normal connection.)


%C command

Enables or disables MNP data compression.

Format:  AT %C<n>

The n parameter enables or disables MNP class 5 data compression:

AT%C0	Disables MNP class 5 data compression.

AT%C1	Enables MNP class 5 data compression (factory setting).

Data will be compressed using MNP class 5 only during reliable transmission with another modem that supports the MNP error control and data compression protocols.


%N command

Sets maximum DTE (computer-to-modem) rate

Format:  AT %N<n>

This command sets the Data Terminal Emulation rate, the rate at which the computer sends data to the modem.  Your communications software normally controls this setting.

The n parameter determines the DTE rate:

AT%N, AT%N0	Connect at the highest DTE rate supported by both modems

AT%N1	Maximum DTE rate is 300 bps (FSK)

AT%N2	Maximum DTE rate is 300 bps (FSK)

AT%N3	Maximum DTE rate is 300 bps (FSK)

AT%N4	Reserved

AT%N5	Maximum DTE rate is 1200 bps (PSK)

AT%N6	Maximum DTE rate is 2400 bps (QAM)


-J command

Specifies whether V.42 automatic error control detection handshaking is used.

Format:  AT -J<n>

The n parameter enables or disables V.42 automatic error control detection handshaking:

AT-J, AT-J0	Disables the modem's generation of (in originate mode) or detection of (in answer mode) error control detection handshaking.

AT-J1	Enables the modem's generation of (in originate mode) or detection of (in answer mode) error control detection handshaking (factory setting).

Some older modems that don't support error control can't tolerate the time needed to do automatic error control detection handshaking.  To improve your ability to connect to one of these older modems or to a V.42 modem, use the \N3 command and disable automatic error control handshaking with the -J0 command.

When you use -J1, the two modems don't need to have the same setting for \N to establish a reliable connection.  With settings of \N3 and \N4, at the beginning of a call, the two modems send each other control characters to determine whether to use MNP or LAPM error control and corresponding data compression.

When you use \N3 or \N4, -J0 tells the modems to skip the V.42 automatic error control detection handshaking sequence and assume LAPM (no MNP connection is made).  To establish an MNP connection with -J0, use \N2.


"H command

Enables or disables V.42bis data compression.

Format:  AT "H<n>

Values for n are:

AT"H, AT"H0	Disables V.42bis data compression.

AT"H1	Same as "H3.

AT"H2	Same as "H3.

AT"H3	Enables V.42bis data compression bidirectionally.  The modem can send, receive, and decode data compressed using the V.42bis data compression protocol (factory setting).


Configuration commands and S registers

Choose one of the following links for more information or for descriptions of the commands that set and retrieve the modem's configuration settings:

About configuration settings

S Registers

Table of configuration parameters

&F<n>	Restores factory configuration profile

&V	Views active configuration

&W<n>	Writes active configuration to nonvolatile memory

&Y<n>	Recalls profile to use when modem is powered up

S<r>	S Register read/write commands

Z<n>	Resets to configuration n


About configuration settings

The modem's configuration settings are stored in S registers.  A subset of the S registers is stored in nonvolatile RAM (random access memory), so you can save the contents of the S registers and use them each time you turn on your computer.

When you issue a modem command to change one of the operating characteristics (such as turning the speaker on or off), the modem changes the values in the S registers to reflect your changes.  The current settings of the S registers are called the active configuration profile.

When you install the faxmodem, the modem establishes the active configuration profile by setting the S registers to initial values.  It gets some of these initial values from the modem's ROM (read-only memory), and it gets others from nonvolatile RAM (NVRAM).  The difference between ROM and NVRAM is that the values in ROM are fixed:  whenever you turn on the computer, the original values are loaded into the S registers.  On the other hand, you can change the values that are stored in NVRAM, and the modem will remember your changes the next time you turn on the computer.  See the &W command for information about changing the values stored in NVRAM.

See the Table of Configuration Parameters for a list of the parameters and their factory settings.  The table also indicates which parameters are initialized from NVRAM, so that you can change or save their initial values.


Table of configuration parameters

Parameter	Factory Setting	Initialized from NVRAM	Associated Command or S Register
Communication rate	9600bps	yes	S23
1200 bps protocol	Bell 212A	yes	B1
Parity	None	yes	S23
Automatic answer	Disabled (ring count=0)	yes	S0=0
Echo	On	yes	E1
Result codes enabled	All	yes	X4
Result codes	Verbal	yes	V1
Wait for dial tone before dialing	Enabled	yes	X4
Busy signal detect	Enabled	yes	X4
Pulse dial make/break ratio	39/61	yes	&P0
Tone dialing speed	70 milliseconds	yes	S11=70
Test timer time-out	0 seconds	yes	S18=0
DSR option	DSR always on	yes	&S0
DTR option	DTR disconnects modem	yes	&D2
Long space disconnect	Disabled	yes	Y0
Speaker	Enabled and on	yes	M1
Speaker volume	Low	yes	L2
Guard tone	Disabled	yes	&G0
Minimum DTR pulse width	0.05 seconds	yes	S25=5
Escape sequence character	43	no	S2=43
Carriage return character	13	no	S3=13
Line feed character	10	no	S4=10
Backspace character	08	no	S5=8
Wait before blind dialing	2 seconds	no	S6=2
Wait for carrier after dialing	30 seconds	yes	S7=30
Dial pause (comma)	2 seconds	no	S8=2
Carrier detect response time	0.6 seconds	no	S9=6
Lost carrier to hangup delay	1.4 seconds	no	S10=14
Escape sequence guard time	1.0 second	no	S12=50
Data carrier detect (DCD)	DCD on only when modem detects carrier	yes	&C1
Maximum MNP block size	256 bytes	yes	\A3
Auto-reliable buffer	Disabled	yes	\C0
Modem-to-modem flow control	Disabled	yes	\G0
Bps rate adjust	Disabled	yes	\J0
Break control	n=5	yes	\K5
Operating mode	Auto-reliable mode	yes	\N3
Inactivity timer	n=0	yes	\T0
Serial port flow control enabled	CTS/RTS control	yes	\Q3
Show error control /data compression	Show full information	yes	\V2
XON/XOFF pass through	Don't pass through	yes	\X0
Auto-reliable fallback character	n=13 (carriage return)	yes	%A13
Data compression	Enabled	yes	%C1
Auto retrain	Enabled	yes	%E1
Error control detection phase selection	Enabled	yes	-J1
V.42bis data compression selection	Enable bidirectional compression	yes	"H3


&F command

Restores factory configuration profile from ROM.

In addition to storing a copy of your current configuration settings in nonvolatile RAM (NVRAM) the modem also has a copy of the original factory settings in ROM.  The &F command lets you restore the modem to its initial factory settings by copying the information from ROM into the S registers.  Unlike the Z command, the &F command restores all the S registers, not just those stored in NVRAM.

Format:  AT &F

The Table of Configuration Parameters lists the values restored by the &F command.


&V command

Displays active and stored configuration profiles.

The &V command reports the active configuration profile of the modem, the two stored configuration profiles (stored with the &W command), and the phone number(s) stored by the &Z command.

Format:  AT &V


&W command

Writes the active configuration profile to nonvolatile RAM (NVRAM).

The &W command writes a subset of the parameters for the modem's active configuration profile into the modem's NVRAM. The information in NVRAM is retained (even when you turn off the modem) and can be recalled later using the Z command.

Format:  AT &W<n>

The n parameter lets you save two configurations (0 or 1).  If you don't specify a value for n, the configuration is saved as 0.

The &W command saves these S registers:

S0	S7	S11	S14	S18

S21	S22	S23	S25	S26

S27	S31

The &W command also saves the settings for these commands:

B	E	L	M	P

Q	T	V	X	Y

&C	&D	&G	&L	&M

&P	&Q	&T4	&T5	&X

\A	\C	\G	\J	\K

\N	\Q	\T	\V	\X

-J	%A	%C	"H


&Y command

Determines which stored configuration profile is restored automatically when you turn on the modem.

Format:  AT &Y<n>

The n parameter (0 or 1) determines which stored profile is restored:

AT&Y, AT&Y0	Designates that profile 0 (previously saved using &W0) is used at startup (factory setting).

AT&Y1	Designates that profile 1 (previously saved using &W1) is used at startup.


Z command

Restores the configuration profile from nonvolatile RAM (NVRAM).

The Z command resets the modem's configuration profile by copying the profile information stored in NVRAM to the corresponding S registers and restoring the other parameters to their factory settings.

Format:  AT Z<n>

The n parameter (0 or 1) selects the configuration profile you want to restore.  (To save a configuration profile in NVRAM, use the &W command.)

The Z command restores the following S registers to the values they had when you last invoked the &W command (or to their original values if you never invoked the &W command):

S0	S7	S11	S14	S18	S21

S22	S23	S25	S26	S27	S31

It also restores the settings of these commands:

B	E	L	M	P

Q	T	V	X	Y

&C	&D	&G	&L	&M

&P	&Q	&T4	&T5	&X

\A	\C	\G	\J	\K

\N	\Q	\T	\V	\X

-J	%A	%C	"H

The Table of Configuration Parameters shows the parameters that are initialized from NVRAM.

The Table of S Registers summarizes which S registers control which parameters.


S command

Reads and writes S registers.

Format to read:  AT S<n>?

Format to write:  AT S<n>=<value>

____________
See also

S registers

Reading S registers

Writing S registers

Specifying S registers

Table of S registers


S Registers
Commands and S registers

There are two kinds of AT commands:

•	commands that your modem acts on immediately

•	commands that change modem settings

The commands that your modem acts on immediately control functions like dialing a phone number, hanging up, and answering an incoming call.  The modem automatically adjusts its settings to match these settings, then stores the settings in its random access memory (RAM). The modem maintains the settings until it receives another AT attention code or until you turn off the modem.

The second kind of AT commands changes modem settings, like how long to wait for an answer after dialing and how many times the modem rings before answering an incoming call.  The modem stores the settings in special locations in the modem memory called S registers.  The modem maintains the settings until it receives another AT command to change the settings.

You can read and write the S registers directly, using the S command.  You probably won't need to do this often, because most of the modem features are associated with specific AT commands.  But some of the S registers control features that aren't available with other modem commands.

The Table of S Register Contents summarizes the features that each S register controls and lists the commands (if any) associated with the register.  It also provides links to detailed descriptions of each individual register.

____________
See also

Reading S registers

Writing to S registers

Specifying S registers

Table of S registers


Reading S registers

Use the S command to read the contents of an S register.

Format:  AT S<n>?

The n parameter is a number from 0 to 28 that indicates the S register you want to read.

In response to the S command, the modem displays a three-digit decimal number indicating the contents of the requested register.  It also displays "OK" on the next line.

Example:	This command reads the contents of register S2:

ATS2?

The modem responds:

043

OK

Example:	You can place multiple read commands on the same line.  In this case, the modem displays the contents of all the registers you request, separated by a carriage return and line feed.  This command reads the contents of S0 and S2:

ATS0?S2?

The modem responds:

003

043

OK


Writing to S registers

Use the S command to write values to (set) S registers.

Format:  AT S<n>=value

The n parameter is a number from 0 to 28 that indicates the S register you want to write to.

The value parameter is the value you want to set the S register to.  You can set any of the S registers to a value from 0 to 255.  The range of valid values, however, is not always 0 to 255.  For some registers, setting the register to a value greater than its allowable range can cause the modem to operate incorrectly.

The Table of S Registers and the detailed register descriptions give the valid range for each register.

Example:	This command sets the S0 register to 4:

ATS0=4

The modem responds:

OK


Specifying S registers

The modem keeps track of the last S register you read from or wrote to.  So, if you want to perform another read or write operation on the same register, you can do so without specifying its name.

•	To read the last S register you referred to, you can omit the S<n> part of the command and use only the ?.

•	To write the last S register you referred to, you can omit the S<n> part of the command and use only the =value.

You can also make one of the S registers the current register without reading or writing it.  Do this by issuing the S<n> command without the =.  Then you can read or write that register without referring to it specifically.

Example:	This command sets S0 as the current register:

ATS0

The modem responds:

OK

This command sets S0 to 3:

AT=3

The modem responds:

OK

This command reads the S0 register:

AT?

The modem responds:

003

OK


Table of S registers

For a detailed description of an S register, choose the highlighted register name below.

*	The contents of the registers marked with an asterisk (*) are stored in nonvolatile RAM.  If you change the registers, you can store the changes permanently with the &W command.

REGISTER	RANGE	FACTORY	DESCRIPTION
SETTING

S0*	0-255 rings	0	Modem auto answer

S1	0-255 rings	0	Ring count

S2	0-127 ASCII	43	Escape sequence character

S3	0-127 ASCII	13	Carriage return character

S4	0-127 ASCII	10	Line feed character

S5	0-32, 127 ASCII	8	Backspace character

S6	0-255 sec	2	Time to wait before blind dialing

S7*	0-255 sec	30	Time to wait for carrier after dialing

S8	0-255 sec	2	Time to pause for each comma

S9	0-255 1/10 sec	5	Carrier detect response time

S10	0-255 1/10 sec	14	Delay between lost carrier and hang up

S11*	50-255	70	Dialing speed
1/1000 sec

S12	0,20-255 c	50	Escape sequence guard time
1/50 se

S13	N/A	N/A	Not used

S14*	N/A	N/A	Bit-mapped options

S15	N/A	N/A	Not used

S16	N/A	0	Modem test options

S17	N/A	N/A	Not used

S18*	0-255 sec	0	Maximum time for diagnostic tests

S19	N/A	N/A	Not used

S20	N/A	N/A	Not used

S21*	N/A	Bit-mapped options

S22*	N/A	Bit-mapped options

S23*	N/A	25	Bit-mapped options

S24	N/A	N/A	Not used

S25*	0-255 	5	Time DTR must remain off
1/100 sec

S26	N/A	N/A	Not used

S27*	N/A	N/A	Bit-mapped options

S28	0-255 seconds	N/A	Bit-mapped options


S0 Register -- Modem auto answer

The value in this register indicates whether the modem will answer a call.  Setting S0 to 0 disables the modem's auto answer capability.  Setting S0 to any valid nonzero number causes the modem to answer on the number of rings specified in your communications software.

Valid range:  0 to 255

Factory setting:  0


S1 Register -- Ring count

This is a read-only register that the modem increments each time it detects a ring signal on the phone line.  The modem clears the S1 value if no rings occur for eight seconds.

Valid range:  0 to 255 rings

Factory setting:  0


S2 Register -- Escape sequence character

The S2 register holds the ASCII value of the escape sequence character.  This is the character you can enter to return the modem from online to command mode.  The factory setting (43) represents the + character.

Although you can set S2 to any value from 0 to 255, values greater than 127 disable the escape sequence feature.  In this situation, the only way the modem can return from online to command mode is by having the remote modem hang up (causing an on-to-off transition of the DTR signal) while the &D command is set to &D1, &D2, or &D3.

Valid range:  0 to 127

Factory setting:  43 (ASCII +)


S3 Register -- Carriage return character

The S3 register holds the ASCII value of the carriage return character.  This character terminates both command lines and result codes.

Valid range:  0 to 127

Factory setting:  13 (ASCII carriage return character)


S4 Register -- Line feed character

The S4 register holds the ASCII value of the line feed character.  The modem sends this character, following the carriage return character, after displaying each verbal result code.

Valid range:  0 to 127

Factory setting:  10   (ASCII line feed character)


S5 Register -- Backspace character

The S5 register holds the ASCII value of the backspace character.  When entered, the backspace character blanks the character just before the cursor, moves the cursor back one character, and deletes the last character in the command buffer.

Don't set the backspace character to a printable ASCII character (ASCII codes 33 through 126).  If you do, the modem won't recognize the character as anything but a backspace character.

The modem processes the backspace character by performing these operations:

•	Echoes the backspace character to the screen

•	Sends an ASCII space character to the screen

•	Sends another backspace character to the screen

Because the modem sends three characters for each backspace character you type, the backspace takes three times as long to process as any other character.  Because of the extra time required, you should not enter multiple backspace characters back-to-back when in command mode.  If you do, the modem might not be able to handle them.  This situation can prevent the repeat key function from working with the backspace key.

Valid range:  0 through 32, 127

Factory setting:  08   (ASCII backspace character)


S6 Register -- Time to wait before blind dialing

The value in the S6 register specifies the ime the modem waits after picking up the phone before dialing the number.  The purpose of this delay is to wait for a dial tone. The effect of the value in the S6 register depends on the setting of the X command.

If you invoke the X0, X1, or X3 command, the modem waits for the amount of time specified in the S6 register, even if a dial tone occurs before that.  Even though S6 can be set to any value between 0 and 255 seconds, the modem always waits at least two seconds, even if you set S6 to 0 or 1.

If you invoke the X2 or X4 command (X4 is the factory setting), the modem disregards the value in the S6 register. Instead, it waits for five seconds, then checks for a dial tone.  If the dial tone is present, the modem dials the number immediately.  If no dial tone is present, the modem issues the NO DIALTONE result code and hangs up.

Valid range:  0 to 255 seconds

Factory setting:  2 seconds


S7 Register -- Wait for carrier after dialing

If you use the X command in the extended result code setting of X3 or X4 (X4 is the factory setting), the modem in originate mode waits for an answer tone from the remote modem. The value in S7 specifies the amount of time the modem will wait.

The modem also uses the value in S7 as the amount of time to wait for completion of the handshake with the remote modem before hanging up.  Because the S7 timer is reset once an answer tone from the remote modem is detected, the combination of answer-tone waiting and handshake-completion waiting can result in a total wait time that is twice as long as the value specified in S7.

When the modem is answering a call, it uses the value in S7 as the time to wait for a carrier only.

Also, the value in the S7 register determines how long to wait for a subsequent dial tone when the W dial modifier is included.  It doesn't affect the time the modem waits for a dial tone after initially going off-hook (the S6 register governs that).  The value in S7 applies to a subsequent dial tone (such as dialing 9 for an outside line and waiting for another dial tone).

Valid range:  0 to 255 seconds

Factory setting:  30 seconds


S8 Register -- Time to pause for each comma

When you include the comma (,) dial modifier in a phone number you're dialing with the D command, the modem pauses before dialing the numbers after the comma (,).  The value in S8 specifies the length of time in seconds the modem waits for each comma in the dial string.

Valid range:  0 to 255 seconds

Factory setting:  2 seconds


S9 Register -- Carrier detect response time

The S9 register specifies how long a carrier signal must be present before the modem turns the data carrier detect (DCD) signal on.

The value in S9 affects the time required to recognize a signal as a carrier.  It has no effect once the carrier has been recognized.  Increasing the S9 value increases the time the modem takes to recognize that a carrier is really a carrier, but it decreases the chance that the modem will detect a false carrier, such as one caused by noise from busy signals or voices.

Valid range:  0 to 255 1/10th-second intervals

Factory setting:  5 (0.5 seconds)


S10 Register -- Wait from lost carrier to hang up

The S10 register specifies how long the modem waits after the carrier is lost (the remote modem hangs up) before disconnecting from connections at 300 bps.  A delay lets the modem recover from momentary losses of the carrier without disconnecting.  Specifying the maximum value (255) causes the modem to ignore any carrier losses and to function as if the carrier were always present.  S10 is ignored in V.32 and V.32bis connections.

If the S10 value is smaller than the S9 value, any loss of carrier will cause a disconnect.  This happens when the modem momentarily loses its carrier and then detects it again.  It waits for the time specified in S9 before reconnecting.  If the wait-to-connect time specified in S9 is greater than the wait-to-hang-up time specified in S10, the modem disconnects (hangs up) before it can re-establish the connection.  When S10 is greater than S9, the length of a carrier loss that the modem can tolerate is the difference between S10 and S9.

Valid range:  0 to 255 1/10th-second intervals

Factory setting:  14 (1.4 seconds)


S11 Register -- Dialing speed

The S11 register specifies how quickly numbers are dialed on tone-dial phones (DTMF tone duration).  (For tone-dial phones, dialing speed is determined by the duration of tones and duration of silence between tones.)

Valid range:  50 to 255 milliseconds

Factory setting:  50 milliseconds


S12 Register -- Escape sequence guard time

The S12 register specifies the escape sequence guard time. This is a delay (during which no characters are received) that must occur immediately before and immediately after an escape sequence (+++).  Also, the time between escape-code characters must be less than the guard time.  If the time before and after the escape sequence isn't long enough, or if the time between escape characters is too long, the modem won't recognize the escape sequence and won't switch the modem from online to command mode.

If you specify a value of 0, the modem doesn't enforce a guard time.  Thus, when you enter three consecutive escape characters, regardless of the timing, the modem will switch to command mode.  If you wish to select a guard time, you must use a minimum value of 20.

Valid range:  0 to 255 1/50th-second (20-millisecond) intervals

Factory setting:  50 (1 second)


S14 Register -- Bit-mapped options

The individual bits in the S14 register control the settings of several modem options.  To determine the current settings of the bits in S14, read the register (command = ATS14?) and translate the resulting decimal number into a binary value.  To change the settings of the bits in S14, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS14 = decimal value).  These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bit 0	Reserved (factory setting = 1).

Bit 1	Echo mode; see the E command.

0	Echo disabled.

1	Echo enabled (factory setting).

Bit 2	Result codes; see the Q command.

0	Result codes enabled (factory setting).

1	Result codes disabled.

Bit 3	Verbal or numeric result codes; see the V command.

0	Numeric result codes

1	Verbal result codes (factory setting)

Bit 4	Reserved.

Bit 5	Pulse or tone dial; see the P and T dial modifiers.

0	Tone dial (factory setting).

1	Pulse dial.  This bit remains set or cleared based on the most recently used P or T modifier in the dial string of a D (dial) command.  A P sets the bit, and a T clears the bit.  Subsequent D commands that omit the P or T modifiers will use the dialing method indicated by the current setting of the bit.

Bit 6	Reserved.

Bit 7	Originate or answer mode; see the A command, the D command, and the R dial modifier.

0	Answer mode.

1	Originate mode (factory setting).


S16 Register -- Modem test options
S16 Register -- Auto-retrain options

Bit 2 in the S16 register controls the auto-retrain option setting.  This register isn't saved in nonvolatile RAM.  To determine the current settings of the bits in S16, read the register (command = ATS16?) and translate the resulting decimal number into a binary value.  To change the settings of the bits in S16, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS16 = decimal value).

The bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bit 0	Reserved.

Bit 1	Reserved.

Bit 2	Auto-retrain setting; see the %E command.

0	Retrain disabled.

1	Retrain enabled (factory setting).

Bits 3-7	Reserved.


S18 Register -- Maximum time for diagnostic tests

The S18 register sets the maximum time that the diagnostic tests will run.  Unless you stop a diagnostic test by invoking the &T0 command, the test will remain active for the amount of time specified in the S18 register.  When the time expires, the modem stops the test.

Specifying a value of 0 disables the test timer.  In this case, any diagnostic test will continue until you enter the &T0 command to stop it.

Valid range:  0 to 255 seconds

Factory setting:  0 (timer is disabled)


S21 Register -- Bit-mapped options

The individual bits in the S21 register indicate the settings of several modem options.  To determine the current settings of the bits in S21, read the register (command = ATS21?) and translate the resulting decimal number into a binary value.  To change the settings of the bits in S21, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS21 = decimal value).

These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bit 0	Reserved.

Bit 1	Reserved.

Bit 2	Not used

Bits 4,3	DTR options; see the &D command.

0	Modem ignores DTR.

1	Modem returns to command state when on-to-off transition of DTR occurs.

2	Modem hangs up when on-to-off transition of DTR occurs (factory setting).

3	Modem initializes when on-to-off transition of DTR occurs.

Bits 5	DCD options; see the &C command

0	DCD always on.

1	DCD on indicates valid data carrier (factory setting).

2	DCD Unix compatibility.

Bit 6	Data set ready (DSR) options; see the &S command.

0	DSR always on (factory setting).

1	DSR always off.

Bit 7	Long space disconnect; see the Y command.

0	Disabled (factory setting).

1	Enabled.


S22 Register -- Bit-mapped options

The individual bits in the S22 register indicate the settings of several modem options.  To determine the current settings of the bits in S22, read this register (command = ATS22?) and translate the resulting decimal number into a binary value.  To change the settings of the bits in S22, determine a binary value that sets and clears the appropriate bits, converting that value to a decimal number, and writing the decimal number into the register (ATS22 = decimal value).  These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

BIT	DESCRIPTION

Bits 1,0	Speaker volume; see the L command

0	Very low volume

1	Low volume

2	Medium volume (factory setting)

3	High volume

Bits 3,2	Speaker on or off; see the M command

0	Speaker always off

1	Speaker on until modem detects carrier (factory setting)

2	Speaker always on.

3	Speaker off when modem detects carrier and during dialing.

Bits 6,5,4	Result code options; see the X command.

0	The modem goes off-hook, waits for the time specified in S6, and dials regardless of the presence or absence of a dial tone.  It sends a CONNECT message when the connection is established (X0 command).

1	Undefined.

2	Undefined.

3	Same as option 0, except the modem waits up to five seconds for a dial tone before dialing, and it can detect a busy signal and return a BUSY code (X5 command).

4	The modem goes off-hook, waits for the time specified in S6, and dials regardless of the presence or absence of a dial tone.  It sends a CONNECT, CONNECT 1200, or CONNECT 2400 message when the connection is established (X1 command).

5	Same as option 4, except the modem waits up to five seconds for a dial tone before dialing (X2 command).

6	Same as option 4, except the modem can detect a busy signal and return the BUSY code (X3 command).

7	Same as option 4, except the modem waits up to five seconds for a dial tone and can detect a busy signal (X4 command) (factory setting).

Bit 7	Make/break pulse dial ratio; see &P command.

0	39/61 ratio, used in the United States and Canada (factory setting).

1	 33/67 ratio, used in the United Kingdom and Hong Kong.


S23 Register -- Bit-mapped options

The individual bits in the S23 register indicate the settings of several modem options.  To determine the current settings of the bits in S23, read this register (command = ATS23=?) and translate the resulting decimal number into a binary value.  To change the settings of the bits in S23, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS23 = decimal number).  Although bits 1 through 5 can be set to any value, if an AT command is entered they indicate the communication parameters of the AT command.  These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bits 3,2,1,0	Serial communication rate (DTE rate); see the AT attention code.  These bits in conjunction with bit 1 of S21 indicate the serial data communication rate of the modem.

When bit 1 of S21 is set to 0, bits 1, 2, and 3 of S23 indicate the current communications rate as follows:

0	300 bps

1	1200 bps

2	2400 bps

3	4800 bps

5	9600 bps

6	19200 bps

7	38400 bps

8	57600 bps

Bits 5,4	Parity; see the AT attention code

0	Even parity (factory setting)

1	Space parity

2	Odd parity

3	Mark parity/no parity

Bits 7,6	Guard tones; see the &G command

0	No guard tones (factory setting)

1	550-Hz guard tone

2	1800-Hz guard tone

3	Reserved


S25 Register -- Time DTR must remain off

The S25 register specifies how long a change in DTR (either on or off) must persist before the modem recognizes the change.  See the &D command.

The S25 value is interpreted as units of 1/100th seconds.

Valid range:  0 to 255 1/100th seconds

Factory setting:  5 (.05 seconds)


S27 Register -- Bit-mapped options

Bits 4 through 7 in the S27 register indicate the setting of the modem communication rate.  This is the rate your modem uses to communicate with another modem, also called the DCE rate.

Read the register to determine the current settings (command = ATS27=?), then translate the resulting decimal number into a binary value.  To change the settings of the bits in S27, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS27 = decimal value).  These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bits 0-3	Reserved.

Bits 7,6,5,4	Modem communications rate.

0	300 bps

1	1200 bps

2	2400 bps

3	Reserved

4	4800 bps

5	9600 bps

6-11	Reserved

12	7200 bps

13	12000 bps

14	14400 bps


S28 Register -- Bit-mapped options

Bits 4 through 7 in the S28 register indicate the settings for your modem's communications protocol.

Read the register to determine the current settings (command = ATS28=?), then translate the resulting decimal number into a binary value.  To change the settings of the bits in S28, determine a binary value that sets and clears the appropriate bits, convert that value to a decimal number, and write the decimal number into the register (ATS28 = decimal value).

These are the bits and their corresponding options:

Bits:	7	6	5	4	3	2	1	0

_____________________________________________________________________________________
BIT	DESCRIPTION

Bits 0-3	Reserved

Bits 4-7	Modem communications protocol.  For more information, see the B command.

0	CCITT compatibility (same as B0)

1	Bell compatibility (same as B1)--(factory setting)

2	Auto-mode protocols (same as B2)

3	Reserved

4	Bell 103 protocol (same as B4)

5	V.22/Bell 212A protocol (same as B5)

6	V.22bis protocol (same as B6)

7	V.32 at 4800 bps protocol (same as B7)

8	V.32 at 9600 bps protocol (same as B8)

9	V.32bis protocol (same as B9)


Using diagnostic commands

The modem includes several commands (I and &T) that run diagnostic tests internal to the modem.  These tests help you isolate the causes of communication failures.

As with all modem commands, you must invoke the diagnostic tests in this section from command mode.

Setting the time a diagnostic test will run

You can set the time a diagnostic test will run by setting register S18 to a nonzero value.  When the time (from 1 to 255 seconds) elapses, the modem automatically halts the test and returns to command mode.  Setting S18 to zero also disables the test timer.  The diagnostic test will then run until you enter the &T0 command to halt the test.

____________
See also

&T command -- Controls diagnostic test commands in direct mode

I command -- Displays the product code and status


&T command

Controls diagnostic test commands in Direct Mode, which is enabled by the \N1 command.

Format:  AT &T<n>

The n parameter controls &T command functions:

&T or &T0 -- Terminates test in progress

&T1 -- Local analog loopback test

&T8 -- Local analog loopback with self-test


AT&T, AT&T0
&T, &T0 command

Terminates any diagnostic test that's in progress.

If you include multiple commands in one command line, make sure the &T0 command is the last one.  The modem ignores commands that follow the &T0 (or &T) command on the same line.

If you're running the local analog loopback test (&T1), you must enter the escape sequence (+++) to return to command mode before invoking the &T0 command.


&T1 command

Initiates a local analog loopback test.

This test checks the data path between the computer and the modem.  It does this by reading information from the transmit data (TD) line and echoing that information back through the receive data (RD) line.  After the test starts, you type information at the keyboard, and the modem echoes that information back to the screen.  If the information appears exactly as you typed it, the modem passes the test.

If the test fails, either your computer or your modem is at fault.

If your modem is online when you invoke this command, the modem will lose the carrier.

The test ends when the time limit in the S18 register expires or when you invoke the &T0 command.  Before invoking the &T0 command, you must enter the escape sequence (usually +++) to return to command mode.

Example:	In this example, you set the test timer to 0 (disabling it) and invoke the local analog loopback test.  After testing the modem, return the modem to command mode and stop the test.

Enter this command to put the modem in diagnostics mode:

AT\N1

Enter this command to set register S18 (the test timer) to 0 and start the test:

AT S18=0 &T1

The modem responds with a connect message or code.  You can now begin entering characters at the keyboard.  The characters should appear on the screen as you type them.  For example:

A rose isn't flower enough.

When you finish testing, enter the escape sequence to return the modem to command mode:

+++

The modem responds with:

OK

End the test with this command:

AT&T0

The modem responds with:

OK

	NOTE:  Be sure to change the \N command back to its original setting.


&T8 command

Initiates a local analog loopback with self-test in accordance with CCITT V.54 recommendation.  This test checks the modem's transmit and receive circuits.

The &T8 command works by causing the modem to send an internally-generated data pattern through the transmit circuit.  The data is not sent to a remote modem but instead is looped back through the modem's receive circuit.  The modem compares the transmitted data with the received data and increments a counter each time it detects an error.

At the end of the test, the modem displays a three-digit number indicating the number of errors that occurred during the test.  If the error count is zero, the modem passed the test.  A nonzero count indicates a problem with your modem.

The modem should be in command mode when you invoke this command.  If the modem is online, the modem will lose the carrier.

The test ends when the time limit in the S18 register expires or when you invoke the &T0 command.

Example:	In this example, you set the test timer to 0 (disabling it) and then invoke the local analog loopback with self-test.  After testing the modem for a while, end the test.

Enter this command to put the modem in diagnostics mode:

AT\N1

Enter this command to set register S18 (the test timer) to 0 and to start the test:

AT S18=0 &T8

If no errors occurred, the modem responds:

000               OK

	NOTE:  Be sure to change the \N command back to its original setting.


I command

Displays the product code and status.

The I command returns your modem's product code or a checksum computed on the modem's ROM.  (Intel Customer Service uses this information to determine the version of your modem and whether the on-board ROM is corrupted.)  This test is not related to the other diagnostic tests described in this section and is not affected by the test timer (the S18 register).

Format: AT I<n>

The n parameter determines what information the command returns:

ATI, ATI0	The modem displays its product code on your computer's monitor.  The product code is three ASCII characters followed by a carriage return and line feed.  The first two characters of the product code indicate the maximum rate at which the modem operates (such as 14 for 14400).  The third character is 9, which indicates an Intel modem.

ATI1	The modem displays a checksum computed on the modem's ROM, followed by a carriage return and line feed.  The checksum is three ASCII numeric characters.  Also displayed are the product code and the version number for your modem's internal program.

ATI2	Computes a checksum and displays the OK or error result code.

ATI3	Displays error correction version and date code.

ATI4	Displays product code, internal program version, modem chip type, and fax class.

ATI5	Same as I4.


Introduction to AT commands

To control your data modem, you use communications software. This software communicates with your data modem using AT commands (attention codes). Usually, you don't need to learn these commands because the communications software lets you use menus and dialog boxes to control the modem.

Sending commands directly to the modem can be useful (for example, to override defaults set by your software, or adjust various aspects of your modem's operation like dialing and answering the phone).

____________
See also

Attention code

Example of an AT command line

Steps for entering AT commands

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Data compression

Initialization strings


Data compression

After your modem establishes a reliable connection with another modem, the transmitted and received data is compressed and decompressed automatically (unless you disabled data compression).

With V.42bis data compression, a file can be compressed to a quarter of its original size.  Computer to computer data transfer will then be up to four times faster than data transmission without data compression.  This can increase the effective throughput for your 14400 bps modem to 57600 bps.

With MNP data compression, a file can be compressed to half of its original size.  Computer to computer data transfer will then be up to two times faster than data transmission without data compression.

Some types of data are more compressible than others, so your throughput depends on the type of data that is transmitted. Data with recognizable patterns is highly compressible.  Files you have already compressed using a software compression program can't be compressed further.

____________
See also

Attention code

Example of an AT command line

Steps for entering AT commands

Operating modes of the modem

The command buffer

Result codes

Commands and S registers

Error control protocol

Initialization strings


Manual dialing

Although the modem can dial the phone, you can dial the phone yourself to talk to someone, and then connect the modem to the line.  Follow these steps to manually dial the phone:

1.	Put your communications software in command mode.

2.	Lift the receiver, wait for a dial tone, then dial the number.  You can talk before connecting the modem.  You should agree on a time to wait (such as 15 seconds) before the other party's modem "answers" your modem.  For more information, see anwering a call.  If the remote modem "answers" your modem before your modem is online, the two modems will not connect.

3.	When you are ready to connect the modem to the line, type:

ATH1

This tells the modem to pick up the line.  Then hang up the phone receiver (the modems won't be able to communicate if any phone receiver connected to the line is off hook).

4.	To tell the modem to go online, type:

ATO

5.	The person on other end should issue the ATA command.  The two modems should now be able to communicate.


&S command

Specifies whether the Data Set Ready (DSR) signal is on or off.  The DSR signal indicates whether the modem is ready to send and receive characters with a remote modem.  Check your communications software manual to determine which setting to use.

Format:  AT &Sn

The n parameter specifies whether the DSR signal is on or off.

AT&S, AT&S0	The modem leaves DSR on whenever the modem is turned on (factory setting).

AT&S1	In accordance with CCITT V.22bis recommendations, DSR is off in command and direct modes and on in data mode.


%E command

The %E command determines whether the modem automatically requests a retrain (or resynchronize the data flow) if it senses problems on the line that may affect data reliability.

Format:  AT %En

The n parameter determines whether the modem will automatically retrain:

AT%E, AT%E0	Sets the modem to not generate retrain requests automatically.

AT%E1	Sets the modem to retrain automatically if it senses line problems (factory setting).


How to control speaker volume

The faxmodem's speaker allows you to listen while your faxmodem dials the phone and connects to a remote modem. You can adjust the volume or turn the speaker on and off using AT commands.

By default, the speaker volume is set to low. To set the volume to medium, use this command:

AT L2

To increase the volume to high, use this command:

AT L3

To return to low volume, use this command:

 	AT L0

By default, the speaker turns on when the faxmodem picks up the phone and turns off when it connects with a remote modem (or hangs up). To turn off the speaker, use this command:

AT M0

To turn on the speaker, use this command:

AT M1


How to dial phone numbers

With most communications software, you can store and dial phone numbers. You can also use the D command to dial the phone. To dial, use this command:

ATD string

The string is a series of characters that can include a phone number and one or more dial modifiers that instruct the modem on how to place the call.

Storing and dialing phone numbers

The data modem can store phone numbers in an area of the modem memory called nonvolatile RAM (NVRAM), and it maintains the phone numbers even if you turn off your computer. To store a phone number, use this command:

AT&Zn=string

Replace n with the location of a phone number in NVRAM; the value of n ranges from 0 to 3.

Once you store phone numbers, use the S dial modifier to dial a number automatically. To dial a stored phone number, use this command:

ATDS=n

Replace n with the location of a phone number in NVRAM; the value of n ranges from 0 to 3.


How to answer a call

Answer manually

Although the data modem can dial and answer the phone automatically, occasionally you may want to dial the phone yourself, talk to someone, and then connect the modem.  To have the modem answer the phone immediately and take control of the phone line in answer mode, use this command:

ATA

Answer automatically

To have the modem answer the phone automatically, set the S0 register to a nonzero value. Use this command:

AT S0=n

Replace n with the number of rings before the modem answers.


How to restore/write/view a configuration profile

To restore factory configuration profile, use this command:

AT &F

To display your modem's active and stored configuration profiles, use this command:

AT &V

To write (save) the active configuration profile to nonvolatile RAM, use this command:

AT &W<n>

The n parameter lets you save two configurations (0 or 1).  If you don't specify a value for n, the configuration is saved as 0.

To determine which stored configuration profile is restored automatically when you turn on the modem, use this command:

AT &Y<n>

The n parameter (0 or 1) determines which stored profile is restored.

To restore a configuration profile from nonvolatile RAM, use this command:

AT Z<n>

The n parameter (0 or 1) selects the configuration profile you want to restore.

____________
See also

About configuration settings

The table of S registers

The table of configuration parameters


How to set echo on/off

To determine whether the modem echoes (sends) the commands to your computer screen as you type them, use this command:

AT E<n>

The n parameter sets the echo mode (1=on).


How to negotiate a Normal/Reliable/Auto-reliable connection

To determine the type of asynchronous connection your modem will try, use the \N command:

Format:  AT \N<n>

The n parameter specifies the type of connection your modem will try:

AT\N0	Forces a normal connection.

AT\N2	Reliable MNP mode.

AT\N3	Auto-reliable LAPM/MNP mode (factory setting).

AT\N4	Reliable LAPM/MNP mode.


&H command

Displays a list of AT commands and their functions.

You can see this list when your are in command mode.  Unlike this online manual, you do not need to leave your communications or terminal emulation software to view this help list.


About ATHELP

This online manual contains information on the AT commands, S registers, and result codes for the Intel High-Speed Faxmodems (144/144 and 96/96).

Version 2.0

Copyright 1993, Intel Corporation.  All rights reserved.

Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497

Intel assumes no responsibility for errors or omissions in this document.  Nor does Intel make any commitment to update the information contained herein.

FaxBACK is a registered trademark of FaxBACK, Inc.  All other brands and trademarks are property of their respective owner.


AT commands - by functional group

Choose a topic to see a list of the related commands and other information.

Making a call

Answering a call

General AT commands

Controlling S registers

Communication options

Configuration settings

Error control and data compression

Result codes

Diagnostic tests


American Bell standard (Bell 103 and 212A)

A standard that specifies the way modems transmit information.  Version 103 of the Bell standard applies to asynchronous  modems transmitting at speeds up to 300 bps.  Version 212A applies to full duplex asynchronous or synchronous modems that transmit at speeds up to 1200 bps.


Asynchronous communication

Communication between computers at irregular intervals.  To handle this kind of communication, the modem adds start and stop bits to each character it sends.  The start bit lets the receiving computer know when a new character has started.  The stop bit indicates the end of the character.


Auto-reliable data connection

Uses LAPM as the primary error control protocol and MNP as a backup protocol.  When the modem makes the connection, it first tries LAPM error control.  If the remote modem can use LAPM, the modems will communicate using LAPM error control.  If the remote modem can't use LAPM, but can use MNP, the modems will communicate using MNP error control.  If the remote modem can't use either, the modems will establish a normal connection.  This definition applies only when the -J1 command is in effect, which is the factory setting.


CCITT

Consultative Committee for International Telephone and Telegraph (CCITT).  An international committee that specifies the way modems and fax machines transmit information to ensure compatibility among modems.  These are the CCITT versions (bis means the second version of a particular standard):

CCITT V.21 -- 300 bps modems

CCITT V.22 -- 600 and 1200 bps modems

CCITT V.22bis -- 2400 bps modems

CCITT V.32 -- 4800 and 9600 bps modems

CCITT V.32bis -- 4800, 7200, 9600, 12000, and 14400 bps modems

CCITT V.42 -- error control

CCITT V.42bis -- data compression

CCITT V.54 -- testing


DTE

Data Terminal Equipment (the computer).  Also Data Terminal Emulation rate, the rate at which the computer sends data to the modem.


LAPM

Link access procedure for modems, an error control protocol specified by CCITT V.42.  LAPM provides error control when your modem is communicating with another modem that supports LAPM.


MNP

Microcom Networking Protocol.  Modems that support MNP can transmit data error-free by resending blocks of data that contain errors until they're received without errors.  MNP class 5 also offers data compression, which increases the speed at which data is transferred.

MNP class 1 (also called block mode) sends data in one direction at a time.  This is about 70 percent as fast as data transmissions using no error correction.

MNP class 2 (also called stream mode) sends data in both directions at the same time.  This is about 84 percent as fast as data transmissions using no error correction.

MNP class 3, in which the sending modem strips the start and stop bits from the data block before sending it.  The receiving modem adds start and stop bits before passing the data to the receiving computer.  About 8 percent faster than data transmissions using no error correction.

MNP class 4 monitors the quality of the connection and streamlines the information in the headers of data blocks.  If the telephone line is relatively noise-free, the modem sends larger blocks of data to increase throughput.  If the telephone line is noisy, the modem sends smaller blocks of data so that less data will have to be resent.  This means more successful transmissions on the first try.  This is about 20 percent faster than data transmissions using no error correction.

MNP class 5 provides data compression.  The sending modem detects redundant data and recodes it to fewer bits to increase the effective throughput.  The receiving modem decompresses the data before passing it to the receiving computer.  This is up to 100 percent faster than data transmissions using no data compression or error correction, depending on the kind of data transmitted.  (Files that are already compressed will seem to contain less redundant data and may therefore take longer to transmit using MNP class 5 than they would if you were using no data compression.)


Protocol

A set of rules that governs how data is transmitted.  To communicate successfully, two modems must use the same protocol.  Protocols usually include error control.


Reliable connection

A connection between two modems where they communicate using an error control protocol (such as LAPM or MNP).


XON/XOFF

A way of controlling the flow of data between a modem and its host computer and between two modems, also called software flow control.  XON stands for "Transmitter On," and XOFF stands for "Transmitter Off."  If the modem receiving data needs time to process the data or do some other task, it sends an XOFF signal to the host computer (or sending modem).  The host computer (or sending modem) then waits until it receives an XON signal before sending more data.


Error control

The encoding of text or data so that a receiving modem can detect and sometimes correct errors in data transmissions.  LAPM and MNP classes 1 through 4 are two different error control protocols.


RS-232C

A standardized system for connecting a device to the serial port of a computer or terminal.  This is the recommended standard of the Electronic Industries Association (EIA) for exchanging information between Data Terminal Equipment (such as computers) and Data Communications Equipment (such as modems).


Throughput

The total useful information processed or communicated in a specified amount of time.  Data compression increases the throughput of your modem by allowing you to send more information in the same number of bits.


BPS

Bits per second, a measurement of the speed at which a device (such as the faxmodem) sends and receives information.  For example, a modem that operates at 2400 bits per second can transfer 2400 binary digits each second.  A character normally consists of seven or eight binary digits, plus the start and stop bits that separate the character from other transmitted characters.


Communications software

Software that provides a human interface to the modem, and sets up modem hardware so that it uses a set of standard protocols to send and receive data.

Examples of DOS-based communications software are HyperACCESS, Smartcom, ProComm, and Crosstalk.


CTS/RTS

Hardware flow control.  CTS means "clear to send", an RS-232C signal that tells the computer it can start sending information.  RTS means "request to send," an RS-232C signal that requests the modem to send data.  RTS initiates any data transmission between the computer (or terminal) and the modem, and is answered by a CTS signal.


Start/stop bits

Signals that define the beginning and end of a data block.


Normal connection

Doesn't use error control but lets error control pass through.  A modem can establish a normal connection and communicate with another modem that has established a normal connection.  You can use serial flow control (set with the \Q command) with a normal connection.  You can also set the serial data rate (with the \J command) to a different speed than that of the modem-to-modem connection.  This definition applies only when the -J1 command is in effect, which is the factory setting.


Data compression

The encoding of text or data so that it takes up less space (fewer bits).  CCITT V.42bis and MNP class 5 are two different data compression protocols.  Data compression allows your modem to transmit more information in a shorter period of time and thus increases your modem's data throughput.


Flow control

The mechanism that regulates the flow of data between two devices.  Modems typically have two methods of flow control:  software flow control (XON/XOFF) and hardware flow control (CTS/RTS).


DTR

Data terminal ready, an RS-232C signal that tells the modem the local computer (or terminal) is ready for data transmission.


DCD

Data carrier detect, an RS-232C signal that indicates the modem is receiving a carrier signal from a remote modem.


Carrier

The base signal used to transmit data across a telephone line.  The modem modulates this signal (alters its frequency or phase) to encode the data to be transmitted.


Answer mode

Used by the modem when answering a call from another computer.  The modem uses originate mode when calling another computer.  Although your modem can operate in either mode, some modems operate only in originate mode.  To communicate with these modems, your modem can switch to answer mode after placing (originating) a call.


ASCII

American Standard Code for Information Interchange. This is a standard method of encoding characters that lets one program or computer understand text generated by another program or computer.


AT commands

The set of industry-standard commands used to control the modem.  Each command line must start with the two-character attention code AT (or at).  AT commands are useful when you need more direct control of your modem than your communications software provides.


Automatic dialing

The modem automatically dials the telephone.  This is in contrast to manual dialing, where a person dials the number.


Auto-answer

The faxmodem automatically answers the phone after a specified number of rings.  This is in contrast to manual answering, where a person sends an AT command to the modem to cause the modem to answer a ringing telephone.  Your communications software may also let you control auto-answer.  See your communications software manual for further information.


Baud rate

The number of symbols transmitted per second.  This is not always the same as the bits-per-second (BPS) rate, because a given symbol, or baud, may have more than one bit.


Buffer

A temporary storage area that the modem uses as it accepts information at one rate and delivers it at another.  For example, a modem sometimes receives data faster than it can process it.  The modem can temporarily store this excess data in a buffer and process it later.


COM ports

Communication ports.  The connectors and accompanying circuitry on your computer that let you connect serial devices (usually serial printers, modems, or pointing devices such as mice) to your computer and communicate with these devices.  To keep track of the ports, DOS assigns them names such as COM1, COM2, COM3, and COM4.


Command mode

One of the two operating modes of the modem, sometimes called local mode or terminal mode.  (The other is online mode.) In command mode, the modem interprets any information it receives from your computer (or terminal) as modem commands.  It tries to perform the commands sent to it, and it returns result codes indicating the results of the commands. The modem enters command mode when you turn on or reboot your computer (or terminal), or when you type the escape sequence (+++) while the modem is in online mode.


Configuration profile

The current operating characteristics of your modem, stored in the modem's S registers.  Whenever you issue a modem command to change one of the operational characteristics (such as turning the speaker on or off), the modem changes the values in the S registers to record your changes.


DCE

Data Communications Equipment (the modem).  DCE rate refers to how fast your modem can send and receive data.


Direct mode

A type of faxmodem connection that is set with the \N1 command, is established for diagnostic tests, and should only be used for that purpose.  When you have completed the diagnostics tests, change the \N command setting back to the setting it was at before you ran the diagnostics.  This definition applies only when the -J1 command is in effect, which is the factory setting.


Dial modifiers

AT commands that you enter along with the AT command D (dial) to further instruct the modem when dialing the telephone.  Dial modifiers specify use of pulse or tone dialing, when and how long to pause between numbers, and whether to dial a stored number.  Select the highlighted area for more information: D command or dial modifiers.


DSR

Data set ready, an RS-232C signal that tells the computer (or terminal) your modem is connected to the telephone line.


Duplex

Modems exchange data in two ways:  half duplex or full duplex.  With half duplex transmissions, only one modem can send data at a time.  Full duplex transmissions allow both modems to send data simultaneously.


Guard time

A period of time during which the modem must not receive characters.  The escape sequence (+++) has a guard time to ensure that data sent from a remote modem isn't interpreted as an escape sequence.  The factory setting for the guard time is one second.  For the modem to interpret an escape code as valid, there must be one second before and one second after the escape sequence in which the modem doesn't receive any characters.


Hayes compatibility

Communications software (and people) communicate with modems using the AT command set.  Modems that support the AT command set are considered Hayes-compatible.


Hook flash

The act of hanging up the telephone for a short period of time (one-half second).  This operation is useful in PBX systems that interpret a hook flash as a signal to perform other services, such as transferring a call.


Interrupt or IRQ

A request-for-attention signal that can be passed to a computer's microprocessor by either hardware or software.  Interrupts (also called interrupt requests or IRQs) are generated by many operations, such as opening a file, starting a program, or receiving a fax.  When the microprocessor receives an interrupt, it suspends its current operations, saves the status of its work, and transfers control to a special routine called an interrupt handler.  The interrupt handler carries out a set of instructions to deal with the interrupt.


I/O

Input/Output.  Input is the data flowing into your computer, and output is the data flowing out.  See also, I/O address and I/O port .


I/O address, I/O port

A channel through which data is transferred between an input or output device and a computer's microprocessor.  The port appears to the micro-processor as one or more memory addresses that the microprocessor can use to send or receive data. Some ports are dedicated solely to either input or output.


Loopback test

A diagnostic test in which characters that are sent to the modem are immediately sent back from the modem. The computer compares the characters sent with the characters received.


Modem

The term modem is derived from modulator/demodulator. A modem transforms (modulates) a computer's digital signals into analog signals that can be sent across telephone lines.  It also demodulates analog signals it receives from the telephone line, converting them back to digital signals the computer can understand.


Nonvolatile memory

Memory that retains the information stored in it even if you turn off the computer.  There are two kinds: ROM and NVRAM.  ROM is programmed with information at the factory, and you can't change it.  NVRAM is used to store configuration information, and you can change it with modem commands.


NVRAM (Nonvolatile RAM)

One type of nonvolatile memory.  NVRAM is used to store configuration information, and you can change it with modem commands.  See also Nonvolatile memory .


Off-hook

This is the condition of the telephone line that corresponds to picking up the receiver.  A modem creates an off-hook condition when it tries to communicate on a telephone line.


On-hook

This is the condition of the telephone line that corresponds to the receiver being on the hook or not in use.  A modem creates an on-hook condition to break its connection with a telephone line.


Online mode

One of the two operating modes of the modem, also called data mode.  (This mode contrasts with command mode.)  In online mode, the modem interprets all information sent to it as data, not commands.  The only exception is the escape sequence (+++), which returns the modem to command mode without breaking the connection.  The modem is in online mode when it makes a connection with a remote modem, or when you enter the O command to return to a previously established connection.


Originate mode

The mode used by your modem when it calls another computer.  See also answer mode .


Parity

A data-encoding scheme that computers (and terminals) use to check the validity of transmitted characters. This scheme adds an extra bit to each character, which the transmitting computer sets or clears based on the type of parity the computers agree to use (odd or even).  For example, when computers use even parity, the transmitting computer sets or clears the parity bit so that an even number of bits is present each character it transmits.  The receiving computer checks each character and displays a parity error message if any character received has an odd number of bits set.


PBX

Private Branch Exchange, a switchboard that handles many telephone lines.


Pulse dialing

One of two methods of dialing the telephone (the other is tone dialing).  With pulse dialing, the modem sends pulses to represent the telephone numbers (one pulse for a one, two pulses for a two, etc.).  You can hear the pulses through the handset as clicks.  Pulse dialing is normally associated with rotary-dial phones.


Result codes

When you enter most modem commands, the modem displays a message on your screen, called a result code, that tells you the results of the command. Your modem's factory setting is: result codes are verbal (words that describe the result conditions). You can also set the modem to display corresponding numbers instead of words (numeric result codes).


Retrain

Intel high-speed modems can automatically retrain themselves (during an active connection) to accommodate changes in signal strength or noise on the telephone line.

When your modem retrains, it attempts to improve data reception by:

   S10 Readjusting its internal signal filters.

   S10 Renegotiating its data transmission rate.


Serial port

A serial port is a connector to which you can attach a serial device such as a printer, a mouse, or a modem.  See also COM ports .


Tone dialing

Tone dialing is one of two methods of dialing the telephone (the other is pulse dialing).  With tone dialing, the modem sends tones of different frequencies to represent the telephone numbers.  Tone dialing is normally associated with push-button (touch-tone) phones and is also called Dual Tone Multi-Frequency (DTMF) dialing.


Reaching Technical Support
How to contact Intel customer support

If you are unable to find answers to your questions using the Intel High-Speed Faxmodem Owner's Guide or using online help, please contact us directly, using the Intel phone numbers shown below.  To learn more about each option for contacting Intel, click on the highlighted option.

Option:
	US & Canada	Europe	Australia	Singapore
Online service
CompuServe	"GO INTELFORUM"	"GO INTELFORUM"	"GO INTELFORUM"	"GO INTELFORUM"
Intel BBS	1-503-645-6275	+44-793-432955	+61-2-975-3066	+65-256-4776
Fax service
FaxBACK	1-503-629-7576	+44-793-432509	+61-2-975-3922	+65-256-5350
FaxUs	1-503-629-7580	+44-793-431166	contact local dealer	contact local dealer
Talk to a Tech	1-503-629-7000	English:	contact local dealer	contact local dealer
		+44-793-431144
		French
		+44-793-421777
		German
		+44-793-421333
You can also write to us at these addresses:

Intel Customer Support, CO3-02 5200 NE Elam Young Parkway Hillsboro, OR 97124-6497 USA	Branded Products Support Centre Intel Corporation (UK), Ltd. Pipers Way Swinden, Wiltshire England  SN3 1RJ


Online Service

Intel's online services let you reach Intel's technical database from your computer, 24 hours a day.  The online services are free (except for the cost of any toll calls), and you can use them to help solve most of your modem problems.

The two online services are:

Intel Bulletin Board Service (BBS):  Get up-to-date product hints and tips, technical and troubleshooting information, and leave questions for Cusomer Support technicians.  Set your modem to the highest speed it supports; 8 data bits; no parity; and 1 stop bit.

CompuServe Information Service:  To reach CompuServe, you'll need a CompuServe account, a modem, and communications software.  You access Intel's CompuServe forum with "GO INTELFORUM".  Software settings are 7 data bits, even parity, and 1 stop bit.


Fax Service

Intel provides fax services that are free (except for the cost of any toll calls) and deliver product support information right to your fax machine.  You can use your fax in two ways:

Intel FaxBACK Service:  Request that technical documents be sent to your fax machine.  Know your fax number before calling.  Call from a touch-tone voice phone.  This service operates 24 hours a day, 7 days a week.

FaxUs:  For specific questions, send us a fax.  We'll do our best to respond by the end of the next business day.  Be sure to include both your fax number and voice telephone number.


Talk to a Tech

For personalized technical support, you can speak with a customer support technician.

When you call, please have the following information available:

Your product's serial number or product code

Your voice and fax phone numbers

Description of your computer hardware (including all add-in boards, their I/O ports, and IRQs) and software

Copies of your CONFIG.SYS and AUTOEXEC.BAT files

Description of the problem and any error messages

In North America, this support is available:
7:00 AM to 5:00 PM	Monday - Wednesday, Friday
7:00 AM to 3:00 PM	Thursday
US Pacific Time

In Europe, this support is available:
09:00 to midnight	in English
09:00 to 17:30	in French
09:00 to 17:30	in German


Help on Using Help

Help is easy to use.  There are four basic steps.

1	Read text, and, if necessary, use scroll bars or PgDn to see more.

2	Click on hotspots for additional information.

3	Use the buttons located at the top of the help window to navigate through the help.

4	On the File menu, choose the Exit command to leave Help and return to the application.


Hotspots

Hotspots are a different color (usually green) and either single or double underlined.

The mouse pointer changes to a pointing hand [image] when you go over a hotspot.  Click on the hotspot to go to the related information.

Some hotspots show the related information in a pop up window.  Press a key to get rid of the pop up window.  Other hotspots move you to another help topic.  Choose the Back button (at the top of the help window) to return from the jump.

Choose one now to see the difference.  Single underlines are pop up windows.  Double underlines  move you to a related screen.


Button Bar

Located at the top of Help window, these buttons provide the most common navigation and search functions.

Move to a list of the main help topics

Search for a word or topic

Return to the last Help screen you saw

Display a window listing the topics you've seen. (Choose any to return there.)


Single underline pop up help

Right!  This is a pop up help.  Click or press any key to make this pop up go away.


Double underline jumps

You clicked on a double underline and jumped to a new topic.  Your original topic is gone...but not for long.  See the Back button at the top of the help window?  Click on that (or press the B key) to return to where you were.