Xircom Ethernet 10/100+Modem 56 - AT Commands

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# Ethernet 10/100+Modem 56
Modem AT Commands

This section provides the following information:

- Introduction to Modem AT Commands
- Special Commands
- AT Command Reference

## Introduction to Modem AT Commands

Modem AT Commands With the exception of the Special Commands, all commands must be preceded by the AT attention code (or command prefix) and terminated by pressing the Enter key.

The modem responds with the result code OK, which means it understands and can execute the command, or with ERROR, which means that the modem does not understand the command or that the command is invalid.

The modem must be in command mode when any command other than the online escape sequence is entered. Commands entered when the modem is in online mode are treated as data and transmitted as such to the modem at the other end of the line.

Some commands are used in coordination with S-Registers.

## Special Commands

#### +++ Online Escape Sequence

The escape sequence is used to switch to command mode from online mode during a session with a remote modem. Type three "plus signs." The escape sequence is not preceded by the AT command prefix, nor does it require the Enter key. The setting of S-Register S2 determines the ASCII character used. S2=43 is the default (the "+" sign). 0-127 are valid. To disable the command, set S2 to a value greater than 127. Use the ATO ("AT" and letter "O") command to return to online mode.

Insert a pause before and after the escape sequence to prevent misinterpretation of the escape sequence as data. Use S-Register S12 to set the length of the pause.

A/ Repeat Last Command

The A/ command causes the modem to repeat the last command string. The command executes as soon as / is typed. It does not require the AT command line prefix, nor does it need to be followed by Enter.

## AT Command Reference

#### A Answer

Typing ATA causes the modem to go off-hook and respond to an incoming call by generating a carrier signal and starting the handshaking process. This must be the only command or the final command in the command line.

If the handshaking process is successful and a connection is established, the normal CONNECT message is displayed. If the carrier signal is not detected within the time specified in S-Register S7, a NO CARRIER result code is displayed.

Bn Select Communications Standard
The ATBn command selects the communication standard (ITU or Bell) to be used by the modem, as follows:

B0 | Use ITU V.22 at 1200bps. B0 selects ITU V.22 at 1200bps and ITU V.21 at 300bps.
B1 | Use Bell 212A at 1200bps. B1 selects Bell 212A at 1200bps and Bell 103J at 300bps.
B2 | Unselect V.23 reverse channel.
B3 | Select V.23 reverse channel.
B15 | Selects V.21 when the modem is at 300bps (same as B0).
B16 | Selects Bell103J when the modem is at 300bps (same as B1).

The ATB1 and ATB16 parameter settings are not available in some countries. Defaults are country-specific.

####

Break (Escape) command See Special Commands.

Cn Carrier Control
The ATCn command, where n is 1, guarantees backward compatibility with communications software that issues the C1 command. C0 is not supported; it may set some modems to "receive only mode."

C0 | Transmit carrier always off (not supported).
C1 | Normal transmit carrier switching.

####

Dn Dial A Telephone Number The ATDn command is used to dial a telephone number. The n represents a dial string consisting of dial digits/characters and dial modifiers (see below) and must not exceed 40 characters. Spaces, hyphens, and parentheses can be used for clarity, but they are ignored by the modem.

The Dial command can be used for either pulse (rotary) or tone dialing. The dial digits/characters are 0 - 9 A B C D # *. The characters A B C D and the symbols # and * represent specific tone pairs and can be used only when tone dialing. These characters and symbols are ignored when pulse dialing is used. Some countries restrict or prohibit the use of some of these characters.

Dial Modifiers

Dial modifiers are recognized by the modem only when they are part of a dial string following the ATD command. Possible dial modifiers are:

P Pulse Dialing Method

The P modifier is used with the Dial command to instruct the modem to pulse dial the telephone number that follows.

S=n Dial a Stored Telephone Number

The S modifier instructs the modem to dial a number that had been previously stored by the use of the AT&Zn=x command. The command to dial a stored telephone number is ATDS=n, where n represents telephone number storage location 0 or 1. For example, ATD P S=1 pulse dials the telephone number written to telephone number storage location 1.

, Delay Processing the Next Character

When the comma (,) modifier is included as part of the dial string following the ATD command, the modem pauses before processing the next character in the dial string. The duration of the pause is dictated by the contents of S-Register S8.

The , modifier is frequently inserted after the digit (usually 9) used to obtain an outside line from a PBX to allow sufficient time for the dial tone to occur before the modem dials the telephone number. The W modifier can be used in place of the comma.

Some countries place restrictions on the amount of time a modem may delay during dialing.

T Tone Dialing Method

The T modifier is used with the Dial command to instruct the modem to tone dial the telephone number that follows. See also the ATT command.

W Wait for Second Dial Tone

The W modifier instructs the modem to wait for a dial tone before processing the remaining characters in the dial string.

! Hook Flash

The ! modifier serves as a switch hook (or hook flash) signal. This causes the modem to hang up (go on-hook) for about 0.5 seconds then return to off-hook (the actual duration of the hook flash varies in different countries).

@ Wait for Quiet Answer

The @ modifier in a dial string instructs the modem to wait for five seconds of silence after dialing the number. If silence is not detected, the modem sends a NO ANSWER result code to the user.

; Return to Command Mode after Dialing

The semicolon (;) dial modifier can be used only at the end of a command line, immediately preceding the Enter, and instructs the modem to return to the command mode immediately after dialing and without breaking the connection with the distant modem.

^ Disable Data Calling Tone Transmission

The ^ modifier in a dial string disables data calling tone for the current call (calling tone is automatically enabled in many countries). This modifier is not available in all countries.

$ Credit Card Tone Detect

The $ modifier in a dial string instructs the modem to wait for a credit card "bong" tone before processing the remaining characters in the dial string.

En Echo Command

The ATEn command, where n represents 0 or 1, determines if the commands you issue through the keyboard to the modem in command mode are displayed (echoed) on your computer's monitor screen.

E0 | Disable echo to the computer.
E1 | Enable echo to the computer (default).

If the commands you type are not displayed on your monitor screen, your software is set to expect character echo from the remote system. You can remedy this by typing in the command ATE1. If the commands you type are displayed on your monitor with the characters duplicated, LLIIKKEETTHHIISS, type in the ATE0 command.

Hn Switch Hook Options

The ATHn command hangs up the modem or prepares it for dialing.

ATH0 | Causes the modem to go on-hook (default).
ATH1 | Causes the modem to go off-hook (this command is restricted in some countries).

In Request ID Information

The ATI command has various options which are used to instruct the modem to provide specific information about itself.

I0 | Displays modem controller firmware revision (same as I3).
I1 | Calculates ROM checksum and displays it on the DTE (for example, 12AB).
I2 | Performs a ROM check and calculates and verifies the checksum. Displays OK or ERROR.
I3 | Displays modem firmware revision information.
I12 | Returns country code (for example, North America).

Ln Monitor Speaker Volume

The ATLn command, where n represents 0, 1, 2, or 3, is listed here for backward compatibility reference only. The volume of the monitor speaker is controlled by the computer, not by the modem.

Mn Speaker On/Off Selection

The ATMn command, where n represents 0, 1, 2, or 3, enables or disables the transmission of sound signals from the modem to the computer speaker. (Sound production also requires that the computer speaker be enabled.)

M0 | Speaker always off.
M1 | Speaker on until data carrier is detected.
M2 | Speaker always on when modem is off-hook.
M3 | Speaker off as digits are dialed, then on after dialing until data carrier is detected.

Nn Negotiation of Handshaking Options

The ATNn command, where n represents 0 or 1, determines whether or not the sending modem performs a negotiated handshake when the speed of the answering modem is different from that of the sending modem.

N0 | When originating or answering, handshake only at the communication standard specified by the contents of S-Register S37 and the ATBn command option selected.
N1 | When originating or answering, handshake only at the communication standard specified by the contents of S-Register S37 and the ATBn command option selected. During handshaking, fall back to a lower speed, if required (default).

On Online Command

If the modem has been switched to command mode, typing in the ATO0 command will return it to the online mode with the existing connection.

O0 | Instructs modem to leave online command mode and return to data mode (see +++ Escape Sequence under Special Commands).
O1 | This setting issues a retrain command before returning to online data mode.
O2 | This setting issues a rate negotiation command before returning to online data mode.

P Select Pulse Dialing

The ATP command instructs the modem to use pulse (rotary) dialing. This mode will remain in force for all dialing procedures unless an ATT command is issued or the dial string contains a T dial modifier.

Qn Result Code Display Options

The setting of the ATQn command, where n represents 0 or 1, determines whether or not result codes (such as OK, CONNECT, RING, NO CARRIER, and ERROR) are displayed on your PC's screen.

Q0 | Display of result codes enabled.
Q1 | Display of result codes disabled.

Repeat command

See Special Commands.

T Select Tone Dialing

The ATT command instructs the modem to use tone dialing. This mode will remain in force for all dialing procedures unless an ATP command is issued or the dial string contains a P dial modifier. Tone dialing is the factory-default setting.

Vn Result Code Format Options

The ATVn command, where n represents 0 or 1, determines if result codes are displayed as numeric (short form) codes or words (long form). Numeric result codes contain only one or two digits and this form could be used, for example, when the modem is controlled by a software terminal emulation program that uses script files. See the list at the beginning of this topic showing result codes in both long and short formats.

Type the command ATV or ATV0 to select numeric result codes. The factory default is to display the result codes as words (ATV1). You should issue an ATV1 command either to reset the factory default after a change has been made or to select the long-form (word) result codes. Negotiation progress messages (extended result codes) are those with a numerical value of 40 or more.

Four other AT commands, two dial modifiers, and an S-Register are also directly involved in the generation and display of result codes. These are the ATQn, ATVn, ATWn, and ATXn commands, the ATDW and ATD@ dial modifiers, and S-Register S95.

Wn Negotiation Progress Message Selection

The ATWn command, where n represents 0, 1, or 2, works in conjunction with S-Register S95 to determine how that subset of the result codes - called negotiation progress messages or extended result codes - will be used to report the type of connection, protocol, and other communication techniques that resulted from handshaking and subsequent negotiation.

The options available to represent n in the ATWn command are:

W0 | CONNECT result code reports DTE speed. If S-Register S95=0, disable the display of all extended result codes.
W1 | CONNECT result code reports DTE speed. If S-Register S95=0, enable the display of CARRIER and PROTOCOL extended result codes only.
W2 | CONNECT result code reports DCE (modem-to-modem) speed. If S-Register S95=0, disable the display of all extended result codes.

Xn Result Code Set/Call Progress Option

The ATXn command, where n represents 0-4, controls how the modem responds to dial tone and busy signals and how it displays CONNECT result codes. The options available to specify with the ATXn command are:

X0 | Result codes 0-4 enabled. Busy detect and dial tone detect disabled.
X1 | Result codes 0-5, and 10 enabled. Busy detect and dial tone detect disabled.
X2 | Result codes 0-6, and 10 enabled. Busy detect disabled and dial tone detect enabled.
X3 | Result codes 0-5, 7, and 10 enabled. Busy detect enabled and dial tone detect disabled.
X4 | Result codes 0-7, and 10 enabled. Busy detect and dial tone detect enabled.

Caution: Some countries do not allow busy detect or dial tone detect to be disabled.

Yn Long Space Disconnect Option

The ATYn command, where n represents 0 or 1, determines whether or not the modem will disconnect a call when it receives a long space (1.6 seconds Break) signal during a V.22bis connection.

Y0 | Disables the long space disconnect facility (supported for backward compatibility reference only).
Y1 | Enables the long space disconnect facility (not supported).

Zn Recall Stored Profile

The ATZn command, where n represents 0, disconnects any call that is currently in progress and reloads the user configuration profile stored in nonvolatile memory as the active configuration profile.

Z0 | Disconnect and reload the profile contained in storage location 0 as the active configuration profile.

&Bn V.32 Automatic Retrain Options

The Xircom modem always retrains. The automatic retrain feature cannot be disabled.

&B0 | Disables the V.32 automatic retrain capability (not supported).
&B1 | Enables the V.32 automatic retrain capability (supported for backward compatibility only).

&Cn Data Carrier Detect (DCD)

The AT&Cn command, where n represents 0 or 1, selects the method by which the modem handles the carrier detect signal.

&C0 | The carrier detect signal is forced on regardless of the condition of the distant modem's carrier.
&C1 | The state of the carrier from the remote modem is monitored. The local modem's DCD signal is on when the remote modem's carrier signal is detected, and off when it is not (default).

&Dn Data Terminal Ready (DTR) Options

The AT&Dn command, where n represents 0-3, controls how the Data Terminal Ready (DTR) signal is used by the modem.

&D0 | Ignore the DTR signal from the computer and treat it as always on.
&D1 | Monitor DTR and, when an ON-to-OFF transition of the DTR signal occurs, switch to command mode, issue an OK result code, and remain connected.
&D2 | Monitor DTR and, when an ON-to-OFF transition of the DTR signal occurs, hang up the line and switch to command mode.
&D3 | Monitor DTR and, when an ON-to-OFF transition of the DTR signal occurs, hang up, reset the modem and switch to the initialization state.

&Fn Load Factory Settings

The AT&F command loads factory default parameters from ROM into the active configuration profile, replacing the parameters stored there. This command must be issued by itself. If it is used with another AT command, its function will be ignored.

&F0 | Recall factory settings as active configuration.
&F5 | Recall factory settings appropriate for ETC mode as active configuration. This command enables ETC operation. It is automatically set upon detection of a cellular phone. The following options are set with &F5:

Local Factory Settings

Function | MTC Implementation
LAPM-only error correction | \N4
Transmit level fixed per cellular phone | S92
Wait for carrier = 90 sec | S7=90
CD loss delay = 10 sec | S10=100
Auto FF/FB enabled | N/A
Start up at 9600bps | S40=2

&Gn V.22bis Guard Tone Selection

This option is for international use only. It is not used in North America. The AT&Gn determines which guard tone, if any, to transmit while in answer mode (transmitting in the high band). The value of n can be 0, 1, or 2. This parameter is set automatically for most countries that require it.

&G0 | No guard tone set.
&G1 | Enable RTS/CTS flow control (default).
&G2 | 1800-Hz guard tone set.

&Jn Auxiliary Relay Option

&J0 | Auxiliary relay is never closed.
&J1 | Not supported (returns ERROR).

&Kn Local Flow Control Options

The AT&Kn command, where n represents 0-4, determines how the flow control between the computer and the local modem is handled.

&K0 | Disable local flow control.
&K3 | Enable RTS/CTS flow control (default).
&K4 | Enable XON/XOFF flow control.

&Mn Communications Mode

The AT&Mn command, where n represents 0-4, determines how the flow control between the computer and the local modem is handled.

&M0 | Asynchronous mode (default; supplied for backward compatibility only).

&Pn Pulse Dial Make-to-Break Ratio Selection

The AT&Pn command, where n represents 0, 1, or 2, controls the ratio of the off-hook (make) to on-hook (break) interval used by the modem when it pulse dials.

&P0 | Selects 39:61 make/break ratio at 10 pps (default - U.S.).
&P1 | Selects 33:67 make/break ratio at 10 pps (default - Japan).
&P2 | Selects 33:67 make/break ratio at 20 pps (option - Japan).

&Qn Asynchronous Communications Mode

&Q0 | Asynchronous mode, buffered (same as \N0).
&Q5 | Error control mode, buffered (default; same as \N3).
&Q6 | Asynchronous mode, buffered (same as \N0).

&Sn Data Set Ready (DSR) Options

The AT&Sn command controls the functions of the modem's DSR circuits.

&S0 | The DSR signal remains on all the time the modem is powered on (default).
&S1 | The DSR signal is on during handshaking and is off when carrier is lost.

&Tn Self-Test Commands

The AT&Tn command allows the user to perform diagnostic tests on the modem.

&T0 | Abort. Stops any test in progress.
&T1 | Local analog loop. this test verifies modem operation, as well as the connection between the modem and computer. The modem must be off-line when this test is run.
&T3 | Local digital loopback test.
&T6 | Remote digital loopback test. This test can verify the integrity of the local modem, the communications link, and the remote modem. The modems must be online with error control disabled when this test is run.

&V View Configuration Profile

The AT&V command displays the contents of the active configuration profile.

&Wn Write Active Profile to Memory

The AT&Wn command, where n is 0, allows you to save a copy of the current active configuration profile to nonvolatile memory. This profile can be restored at any time by using the ATZ command or a power-up reset of the modem.

&Yn Select Stored Profile for Hard Reset

This command is included for compatibility with applications that use the &Y0 command. It does not affect the behavior of the modem.

&Y0 | Select stored profile 0 on power up.
&Y1 | Not supported, returns ERROR.

&Zn=x Store Telephone Number

The AT&Zn=x command is used to store a telephone number for later dialing using the ATDS=n (dial stored number) command. In this command, n is 0 or 1 representing 2 storage locations and x is the stored number. The dial string may contain up to 40 characters.

\Gn Modem Port Flow Control

The AT\Gn command determines whether XON/XOFF flow control will be used.

\G0 | Returns OK for compatibility (default).
\G1 | Not supported; returns ERROR.

\Jn Adjust BPS Rate Control

\J0 | Turn off feature (default).
\J1 | Turn on feature.

\Kn Break Control

The AT\Kn command determines how the modem processes a Break signal received from the local DTE during a connection (online).

\K5 | Modem sends Break to remote modem in sequence with transmitted data, nondestructive/nonexpedited (default).

\Nn Error Mode Control Selection

The AT\Nn command sets the type of error correction supported by the modem when sending or receiving data.

\N0 | Buffered mode. No error control (same as &Q6).
\N1 | Buffered mode (same as \N0).
\N2 | LAPM, MNP or disconnect mode. This is also known as reliable mode.
\N3 | LAPM, MNP, or buffered (default). The modem attempts to connect in LAPM error control mode. If this fails, the modem attempts to connect in MNP mode. If this fails, the modem connects in buffered mode and continues operation. This is also known as V.42 auto-reliable mode (same as &Q5).
\N4 | LAPM or disconnect. The modem attempts to connect in LAPM error control mode. If this fails, the call will be disconnected.
\N5 | MNP or disconnect mode. The modem attempts to connect using MNP 2-4 error control procedures. If this fails, the modem disconnects. This is also known as MNP reliable mode.

\Qn Local Flow Control Selection

The AT\Qn command sets the type of flow control used on the serial port to adjust for differences in modem port speed.

\Q0 | Disables flow control (same as &K0).
\Q1 | Sets flow control to XON/XOFF (same as &K4).
\Q3 | RTS/CTS to DTE (default; same as &K3).

\Tn Inactivity Timer Limit

The AT\Tn command specifies length of time (in minutes) that the modem waits before disconnecting when no data is sent or received. The time period can be set at n = 0 - 255. A setting of zero disables the timer. As an alternative, the timer may be specified in S-Register S30. This function is only applicable in buffer mode.

\Xn XON/XOFF Pass Through

\X0 | Modem process XON/XOFF flow control characters locally (default).
\X1 | Not supported; returns ERROR.

%B View Numbers in Blacklist

If blacklisting is in effect, the AT%B command displays the numbers for which the last call attempted in the past two hours failed. In countries that do not require blacklisting, this command returns ERROR.

%Cn Data Compression Control

The AT%Cn command determines the operation of V.42bis and MNP class 5 data compression. Online changes do not take effect until a disconnect occurs.

%C0 | V.42bis/MNP Class 5 compression disabled (no data compression).
%C1 | MNP Class 5 compression enabled (no V.42bis).
%C2 | V.42bis compression enabled (no MNP Class 5).
%C3 | V.42bis/MNP Class 5 data compression enabled (default).

-Cn Data Calling Tone

Data calling tone is a tone of a certain frequency and cadence specified in V.25 that allows remotes data/fax/voice discrimination. The frequency is 1300 Hz with a cadence of 0.5 seconds on and 2 seconds off.

-C0 | Disables calling tone (default).
-C1 | Enables calling tone.

Caution: Some countries do not permit calling tone to be disabled.

+V90n Enable/Disable V.90 Settings

Syntax: | AT-V.90=<n>
| AT-V90?
| AT-V90=?

This command enables or disables V.90 and changes the downstream rate as follows:

-V90=0 | Disables V.90.
-V90=1 | Disables V.90 autorate (default)
-V90=X | Conrols the downstream rate.
Values of X |
"AT-V90=X" | Downstream Rate
0 | V.90 disabled
1 | Autorate (default)
2 | 28000 bit/s
3 | 29333 bit/s
4 | 30666 bit/s
5 | 32000 bit/s
6 | 33333 bit/s
7 | 34666 bit/s
8 | 36000 bit/s
9 | 37333 bit/s
10 | 38666 bit/s
11 | 40000 bit/s
12 | 41333 bit/s
13 | 42666 bit/s
14 | 44000 bit/s
15 | 45333 bit/s
16 | 46666 bit/s
17 | 48000 bit/s
18 | 49333 bit/s
19 | 50666 bit/s
20 | 52000 bit/s
21 | 53333 bit/s

+GCI Country of Installation

Syntax: | AT+GCI=<T.35 code>
| AT+GCI?
| AT+GCI=?

This command configures the modem for the country of use, selecting operational parameters and ensuring conformity to the requirements of the selected country's telephone network. The +GCI parameter may only be changed when the modem is in an idle state.

<T.35 code> refers to the 8-bit hexadecimal number next to the country in the list below.
Note 1: The Xircom CountrySelect utility is recommended for setting country parameters for modem calls. The CountrySelect utility is accessible after installation at Start, Programs, Xircom Utilities.

Note 2: To determine what countries are supported by your Xircom modem product, run the Xircom CountrySelect utility using Start, Run, Xircom Utilities, CountrySelect, or use the command AT+CGI=?. The AT+CGI=? command will respond with the T.35 codes for the countries supported. The list of <T.35> codes below includes countries supported by this product at time of publication, but not all countries listed are supported by this product.

Caution: For units sold in Japan, Japan has been set as the default country setting. The unit should be set to Japan modem when used in Japan. Use of any other country setting for calls originating in Japan is a violation of local law.

To change the current country selection, use AT+GCI=<T.35 code> (but see Notes 1 and 2 above).

Country | <T.35 code> | Country | <T.35 code>
Argentina | 07 | Mexico | 73
Australia | 09 | Netherlands | 7B
Austria | 0A | New Zealand | 7E
Barbados | 0E | Norway | 82
Belgium | 0F | Panama | 85
Brazil | 16 | Philippines | 89
Canada | 20 | Poland | 8A
China | 26 | Portugal | 8B
Czech Republic | 2E | Puerto Rico | 8C
Denmark | 31 | Russia | B8
Finland | 3C | Singapore | 9C
France | 3D | Slovakia | FC
Germany | 04 | Slovenia | FB
Greece | 46 | South Africa | 9F
Guam | 48 | South Korea | 61
Hong Kong | 50 | Spain | A0
Hungary | 51 | Sweden | A5
Iceland | 52 | Switzerland | A6
India | 53 | Taiwan | FE
Indonesia | 54 | Thailand | A9
Ireland | 57 | Turkey | AE
Israel | 58 | United Kingdom | B4
Italy | 59 | United States | B5
Japan | 00 | Universal | FD
Kuwait | C2 | United Arab Emirates | B3
Liechtenstein | 68 | US Virgin Islands | FA
Luxembourg | 69 | Venezuela | BB
Malaysia | 6C | Vietnam | BC

+MS Modulation Selection

The AT+MS parameter controls data modulations and bit rates that may be negotiated between a local and remote modem. It accepts four subparameters.

Syntax: | AT+MS=<carrier>,<automode>,<0>,<max_rate>,<0>,<max_rx_rate>
| AT+MS?
| AT+MS=?

+MS? | Reports the current settings of subparameters
+MS=? | Displays range of acceptable values for each subparameter
<carrier> | Specifies the preferred modulation to be used in originating or answering a connection. The <carrier> subparameter is an unquoted string of characters. If the <carrier> parameter is specified, the other subparameters will revert to factory defaults. If <carrier> is omitted, any unspecified parameters will keep their current values (for example, AT+MS=,0 or AT+MS=,,,2400).

Values accepted for <carrier> are the following:
V21 ITU-T V.21 (300bps)
V22 ITU-T V.22 (1200bps)
V22B ITU-T V.22bis (2400bps)
V23C ITU-T V.23 with constant carrier (1200/75 or 75/1200bps)
V32 ITU-T V.32 (4800 or 9600bps)
V32B ITU-T V.32bis (4800 - 19200bps)
V34 ITU-T V.34 (2400 - 33600bps)
K56 Lucent/Rockwell K56flex (32000 - 56000bps).
V90C or V90 (28000 - 56000bps).

<automode> | Enables or disables negotiation of an alternative <carrier> if the preferred modulation is not available.
| Values accepted for <automode> are the following: 0 Disabled. Modem will disconnect if it is unable to negotiate a connection with the specified <carrier>. 1 Enabled (default). If the specified <carrier> is unavailable, modem will attempt to negotiate an alternative carrier as appropriate.

<max_rate>

Specifies the highest bit rate at which the modem may establish a connection. For modulations that support only a fixed bit rate (such as V.22bis), <max_rate> has a fixed value to which it defaults. If the default rate or a rate other than zero is specified, the modem will return ERROR. This subparameter accepts the following values: 0, 300 (V21), 1200 (V23), 2200 (V22), 2400 (V22bis), 4800-14400 in a step of 2400 (V32), 4800-19200 in a step of 2400 (V32bis), 2400-33600 in a step of 2400 (V90.K56,V34). If unspecified (set to 0), <max_rate> is determined by the value of <carrier>.
If the <carrier> setting is K56, the <max_rate> subparameter should be left at the default value (zero).

<max_rx_rate> | Specifies the highest bit rate at which the modem may establish a connection. For modulations that support only a fixed bit rate (such as V.22bis), <max_rate> has a fixed value to which it defaults. If the default rate or a rate other than zero is specified, the modem will return ERROR. This subparameter accepts the following values: 300 (V21), 1200 (V23), 2200 (V22), 2400 (V22bis), 4800-14400 (V32), 4800-19200 in a step of 2400 (V32bis), 2400-33600 in a step of 2400 (V34), 32000-56000 in a step of 2000 (K56), 28000-56000 in a step of 1333 (V90).

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