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This reference includes all the commands that are found in industry standards as well as commands that appear in the reference modem designs and specifications that are published by the major modem chipset manufacturers or modem firmware designers.
This section describes AT modem commands that begin with the ampersand "&" prefix character. (Commands with no prefix or a different prefix are described in other sections.)
After a description of the function of the command or option, the "Standards: section will indicate if the described command is compatible with a standard, such as EIA/TIA-602. The section number of the standard that covers the command is included.
The "Compatibility" entry uses the following symbols to indicate which modems the described command is compatible with:
The EIA/TIA-602 standard only specifies three AT commands with ampersand prefixes: &C, &D and &F. All other AT commands with ampersand prefixes derive either from the Hayes Smartmodem 2400, Hayes Ultra 14,400 or are proprietary features of other makers. Subsequently, there are more cases in the ampersand-prefixed commands where a given command does completely different things depending on who made a given modem.
This document cannot include every command available on every modem claiming to be AT Command Set compatible, and the documentation for a specific modem should always be trusted over any other reference when it comes to what commands are available and what actions they perform. For example, a given command may have a completely different function on one brand of modem than on other brands. In cases where conflicts are known, the conflicting commands and their behavior are described below.
The default settings for each command or modifier are marked "(Default)" and in Green. Be aware that different vendors may have a different default value for the same command or S-register. When known, this is documented.
|
&$
(Display Ampersand-prefixed commands) |
On USR/3Com modems, the "&$" command displays a list of the commands
that begin with the ampersand (&) character.
Standards: The "&$" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
|
&A
(Display ARQ Codes) |
On USR/3Com modems, the "&A" command enables or disables AQR Result Codes.
These messages display when the modem enters or returns to Data Mode,
although other commands can override part or all of this display.
Standards: The "&A" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: The "&A" command is used in Sierra modems for an unrelated function. |
|
| Modifiers | Description | |
| &A0 | ARQ Result Codes are disabled. | |
| &A1 | ARQ Result Codes are enabled. | |
| &A2 | ARQ Result Codes are enabled and the V.32 modulation indicator is also displayed. | |
| &A3
(Default) |
ARQ Result Codes are enabled. The V.32 modulation indicatoe and protocol indicators (LAPM/MNP/NONE for Error Control and V.42bis/MNP5 for data compression) are also displayed. | |
|
&A
(Automatic Fall Forward and Fall Back) |
Sierra V.34 modems use the "&A" command to enable or disable the modems
ability to increase or decrease connection speed in response to changing
line conditions.
Standards: The "&A" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - - S - - - Note: The "&A" command is not present on V.32bis and earlier Sierra modems. USR/3Com modems use the "&A" command for unrelated operations. |
|
| Modifiers | Description | |
| &A0 | The modem will not perform fall-forward or fall-back operations. | |
| &A1
(Default) |
The modem will perform fall-forward or fall-back operations as line conditions change. | |
|
&B
(Set DTE Speed) |
On USR/3Com modems, the "&B" command specifies how the DTE transmission
rate is determined.
Standards: The "&B" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: Lucent modems use the "&B" command for unrelated functions. |
|
| Modifiers | Description | |
| &B0 | The DTE speed is variable and adjusts to match the DCE rate when a connection is established. | |
| &B1
(Default) |
The DTE rate is fixed to the speed detected on the DTE for the last command. | |
| &B2 | The DTE rate is fixed in ARQ Data modes and variable in non-ARQ Data modes. | |
|
&B
(V.32 Auto Retrain) |
The "&B" command controls whether the modem performs automatic retrains
during V.32 connections.
Standards: The "&B" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems. See individual option descriptions. |
|
| Modifiers | Description | |
| &B0 |
The modem will not perform automatic retrains during V.32 transmissions
when they are needed needed.
Compatibility: - - - - - - - - - Note: Lucent modems accept and ignore the "&B1" command, but do not accept the &B0 command. |
|
| &B1
(Default) |
The modem will perform automatic retrains during V.32 transmissions
when they are needed needed.
Compatibility: - - - - - - L - Note: Lucent modems accept and ignore the "&B1" command, but do not accept the &B0 command. |
|
|
&C
(Data Carrier Detect) |
The "&C" command instructs the modem as to what (if anything) to report to
the DTE via the Carrier Detect signal (DCD or CD). The command takes
effect immediately.
In the RS-232 standard using DB25 connectors, the CD signal is on Pin 8. This electrical signal is also known as the Received Line Signal Detector (RLSD) and Circuit 109 in related standards. Standards: EIA/TIA-602 6.3.8 (&C0 and &C1 only) Compatibility: Not all options are implemented in all modems. See individual option descriptions. |
|
| Modifiers | Description | |
| &C0 |
The "&C0" command causes the modem to report to the DTE that carrier
is always being detected, even if the modem is on-hook or there is no actual
carrier signal present.
This mode is useful in certain situations when the DTE operating system or application will not allow commands to be sent to the modem when CD detect signal is false on the RS-232 interface, but there can be no carrier on the phone line until the modem has been instructed to establish carrier. Most modern operating systems will allow characters to be transmitted regardless of the state of CD, but may require the CTS or DSR RS-232 signals to be true before characters may be sent. Standards: EIA/TIA-602 6.3.8 Compatibility: 2 4 E R U S L T C |
|
| &C1
(Default) |
The "&C1" command instructs the modem to have the Carrier Detect signal sent
to the DTE by the modem change state generally based on the presence or
absence of carrier between this modem and the remote modem.
There is not a precise relationship between the presence of carrier between DCEs. For example, based on a S register setting, the modem may continue to report the presence of carrier to the DTE when carrier on the telephone line is briefly lost. Other protocol layers operating in the modem may also delay reporting a change in carrier status back to the DTE. See the MNP-3, MNP-4, V.42, V.110, V.120 and V.13 protocols for additional related interactions. Standards: EIA/TIA-602 6.3.8 Compatibility: 2 4 E R U S L T C |
|
| &C2 |
On Sierra V.34 modems, the "&C2" command causes the Carrier Detect signal to
indicate the true state of the remote carrier signal. This means that
any interruption in the carrier received from the remote modem will cause
the DCD line to toggle, even if the modem is able to recover and
continue the data connection without data loss.
Standards: The "&C2" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - - S - - - Note: The "&C2" command is not present on V.32bis and earlier Sierra modems. |
|
| &C2 |
On Telebit modems, the "&C2" command forces the Data Carrier Detect signal to
a TRUE state, execpt when the actual received data carrier goes from a
present to an absent state (disconnect), the Data Carrier Detect signal sent
to the DTE toggles briefly by going FALSE, then TRUE again.
Standards: The "&C2" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - - - - T - Note: The duration DCD FALSE condition is dictated by the "S47" register. |
|
| &C3 |
On Telebit modems, the "&C3" command forces the Carrier Detect signal
sent to the DTE by the modem to be the inverse of the Clear To Send (CTS)
signal.
Standards: The "&C3" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - - - - T - |
|
|
&D
(Data Terminal Ready) |
This command instructs the modem on how to respond in response to the DTE
changing the state of the Data Terminal Ready (DTR) signal.
In the RS-232 standard with DB-25 connectors, the DTR signal is on Pin 20. This electrical signal is also known as Circuit 108 or 108/2 in related standards. Note: Per the EIA/TIA-602 specification, any action that the modem takes is to be performed on the TRUE to FALSE transition of DTR, but some non-compliant modems deviate from this, remaining completely unresponsive to subsequent commands from the DTE and unresponsive to incoming calls until DTR becomes TRUE again. Such behavior is incompatible with the EIA/TIA-602 specification. Standards: EIA/TIA-602 6.3.9 (&D0, &D1, and &D2) Compatibility: Not all options are implemented in all modems. See individual option descriptions. |
|
| Modifiers | Description | |
| &D0
(Default) |
The modem ignores the status of the DTR signal at all times.
Standards: EIA/TIA-602 6.3.9 Compatibility: 2 4 E - U S L T C |
|
| &D0
(Default) |
On Rockwell modems, the "&D0" command behavior varies based on the
settings of other commands. If "&Q0", "&Q5" or "&Q6" is set,
DTR is ignored at all times. If "&Q1" or "&Q4" is set and DTR goes FALSE,
it will cause the modem to go on-hook and auto-answer is still allowed.
If "&Q2" or "&Q3" is set and DTR goes FALSE, it will cause the modem
will go on-hook and auto-answer is disabled until DTR goes TRUE.
The modem ignores the status of the DTR signal at all times.
Standards: Rockwells implementation of "&D0" is not 100% compatible with EIA/TIA-602 6.3.9. Compatibility: - - - R - - - - - |
|
| &D1 |
When DTR changes from TRUE to FALSE, the modem will return to Command
Mode if it was in Data Mode. Any call in progress is undisturbed, and
the behavior is similar to sending the Data Mode Escape character Sequence.
Some modems also require the DTR drop for at least the amount of time
specified by the "S25" register prior to entering Command Mode.
Standards: EIA/TIA-602 6.3.9 (&D1 is optional) Compatibility: 2 4 E - - S L T C Note: USR/3Com modems do not implement this optional command in the EIA/TIA-602 specification. |
|
| &D1 |
On Rockwell modems, the behavior of the "&D1" setting is dependent on
other parameters. If "&Q0", "&Q1", "&Q4", "&Q5", or "&Q6" is set and
DTR goes FALSE, the modem will switch to Command Mode without going on-hook.
If "&Q2" or "&Q3" is set and DTR goes FALSE, the modem goes on-hook,
the modem enters Command Mode and auto-answer is disabled.
Standards: Rockwells implementation of "&D1" is not 100% compatible with EIA/TIA-602 6.3.9. Compatibility: - - - R - - - - - |
|
| &D2
(Default USR/3Com Modems) |
When DTR changes from TRUE to FALSE, the modem will terminate any call in
progress with a complete protocol tear-down, place the modem on-hook and
return to Command Mode. While DTR is FALSE, the modem will not go off-hook
in response to an incoming call, but will report RINGs received if RING
detection is enabled (see the "X" command).
If the "&D3" command is not available on a given modem, this is the second-best preferred setting when modems are used in an auto-answer configuration. The modem may qualify the DTR signal with a timer, typically controlled by the S25 register. (This varies by manufacturer - see the S registers for details.) If the DTR signal goes from TRUE to FALSE, it must remain in FALSE state for at least the amount of time specified by the timer, or else the transition is ignored. This allows the modem to reject noise and other glitches on the DTR signal that might falsely terminate a call in progress. Standards: EIA/TIA-602 6.3.9 Compatibility: 2 4 E R U S L T C Note: "&D2" is the default setting on USR/3Com modems instead of "&D0", the more common default. |
|
| &D3 |
When DTR changes from TRUE to FALSE, the modem will terminate any call in
progress with a complete protocol tear-down, place the modem on-hook and
reset itself, performing steps similar or identical to those in the Z
command. While DTR is FALSE, the modem will not go off-hook in response to
an incoming call, but will report RINGs received if RING detection is enabled
in the post-reset settings (see the "X" command).
The modem may qualify the DTR signal with a timer typically controlled by the S25 register. (This varies by manufacturer - see the S registers for details.) If the DTR signal goes from TRUE to FALSE, it must remain in FALSE state for at least the amount of time specified by the timer, or else the transition is ignored. This allows the modem to reject noise and other glitches on the DTR line that might falsely reset the modem and incorrectly terminate a call in progress. Because "&D3" can guarantee that each incoming call gets a freshly-reset modem, this setting is preferred for most unattended auto-answer modem configurations. Standards: The "&D3" command is not part of the EIA/TIA-602 standard. Compatibility: - 4 - - - S L T C Note: A few modems return an unsolicited "OK" Result Code as a consequence of the "&D3" command when a TRUE to FALSE transition of DTR occurs. This is done prior to rebooting the modem. Also, the typical modem is usually not able to accept subsequent commands for several seconds following a reset. It should be assumed that when &D3 is used, the modem will be briefly unresponsive when DTR transitions from TRUE to FALSE. |
|
| &D3 |
On Rockwell modems, the behavior of the "&D3" command is dependent on
other parameters. If "&Q0", "&Q1", "&Q4", "&Q5", or "&Q6" is set and
DTR goes FALSE, the modem will go on-hook and perform a soft reset. After
the reset is complete, the modem will be in Command Mode.
If "&Q2" or "&Q3" is set and DTR goes FALSE, the modem goes on-hook,
the modem enters Command Mode and auto-answer is disabled.
Standards: The "&D3" command is not part of the EIA/TIA-602 standard. Compatibility: - - - R - - - - - Note: The few modems that do return an unsolicited "OK" Result Code as a consequence of the "&D3" command and a TRUE to FALSE transition of DTR do so prior to rebooting the modem. Also, the modem is typically not actually able to accept subsequent commands for several more seconds. It should be assumed that when &D3 is used, the modem will be briefly unresponsive when DTR transitions from TRUE to FALSE. |
|
|
&F
(Recall Parameters) |
The "&F" command instructs the modem to load a stored configuration into
the modems active register area, forcing all parameters to default
values. The action may also be impacted by any customer-selected
hardware configuration switches or other "manufacturer-defined critera".
So what does all that mean? It means that the "&F" command series may set all or some registers and modem state with pre-defined factory defaults, alterations possibly based on physical jumpers or switches on the modem. Most modems always restore the stored profile #0 in a reset situation, but a few brands allow the customer to specify that a stored profile other than #0 is to be loaded after a modem reset that was not initiated by an explicit command. Certain brands of modems offer multiple "&F" commands, with each loading a factory-provided profile that are considered best for certain types of modem use. None of these are part of the EIA/TIA-602 specification, and should be considered unique to a specific brand and model of modem, possibly even unique to certain firmware versions for a given model of modem. Standards: EIA/TIA-602 6.1.8 (&F0 only - read Note below) Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: The EIA/TIA-602 standard only defined a single command (&F0) which the standard clearly states is to be used to "set parameters to factory defaults". However, many modem makers deviate from this, meaning that a modem reset (either by Z command, a TRUE-to-FALSE transition on DTR when "&D3" is used, or a power reset) followed by a "&F" may be the only way to truly force all modem registers back to their factory settings. This is because some modem makers fail to reset every register and setting in the "&F" command, and many do not store all possible settings in the stored profiles, meaning that they must be re-issued to the modem following a modem reset. The values that are loaded in response to a given "&F" command vary by manufacturer, and sometimes by individual modem model. |
|
| Modifiers | Description | |
| &F0
(Default) |
On Rockwell/Connexant modems, the "&F0" command sets the following factory
defaults:
(some commands and registers may not exist on given modem models)
B1, E1, L2, M1, N1, P, Q0, V1, W0, X4, Y0, &C1, &D0, &G0, &J0, &K3, &L0, &P0, &Q5, &R0, &S0, &T4, &U0, &X0, &Y0, \C0, \G0, \N6, \Q3, \T000, \V1, \X0, %A000, %D1, %E1 There are also undocumented registers that are set to factory defaults. Compatibility: - - - R - - - - - |
|
| &F0
(Default) |
On USR/3Com modems, the "&F0" command sets the "Generic template" factory
defaults. (No other information was provided.)
Compatibility: - - - - U - - - - |
|
| &F0
(Default) |
On Sierra modems, the "&F0" command sets the following factory defaults:
(some commands and registers may not exist on a given modem model)
(V.32bis modems) B1, E1, L2, M1, N1, P, Q0, V1, W0, X4, Y0, &C1, &D0, &G0, &J0, &K3, &L0, &P0, &Q5, &R0, &S0, &T4, &U0, &X0, &Y0, \C0, \G0, \N6, \Q3, \T000, \V1, \X0, %A000, %D1, S0=0, S2=43, S3=13, S4=10, S5=8, S6=2, S7=40, S8=2, S9=6, S10=14, S11=75, S12=40, S14=0xAA, S16=0x00, S18=0, S21=0x20, S22=0x76, S23=0x07, S25=5, S26=1, S27=0x49, S36=7, S37=0, S38=20, S46=138, S48=7, S49=10, S50=200, S63=0, S82=128. (V.34 modems) E1, L2, M1, T, Q0, V1, X1, Y1, &C1, &D0, &R1, &S1, &T0, &U0, &X0, \C2, \F0, \G0, \N3, \Q2, \T001, \V3, %A3, %D1, S0=0, S2=0, S3=43, S4=13, S5=10, S6=2, S7=60, S8=2, S9=6, S10=14, S12=8, S18=75, S25=0, S38=0There are also undocumented registers that are set to factory defaults. Compatibility: - - - - - S - - - |
|
| &F0
(Default) |
On Lucent (formally AT&T Microelectronics) modems, the numeric
parameter is ignored, and a factory configuration to perform "V.42bis
error correction/data compression" is loaded. No other information
was provided.
Compatibility: - - - - - - L - - |
|
| &F0
(Default) |
On Telebit modems, the configuration is loaded according to the settings
of the "S254" register. This setting is used mainly with asynchronous
terminals. (Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q0 V1 X1 Y0 &C0 &D0 &G0 &J0 &L0 &Q0 &R3 &S0 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F0
(Default) |
No information was provided on what default settings are loaded.
Compatibility: - - - - - - - - C |
|
| &F1 |
On Rockwell modems, the "&F1" command restores factory configuration #1.
No other information was provided.
Compatibility: - - - R - - - - - |
|
| &F1 |
On USR/3Com modems, the "&F1" command sets the "Hardware flow control template"
factory defaults. No other information was provided.
Compatibility: - - - - U - - - - |
|
| &F1 |
Sierra V.34 modems list this command only as "Reserved for factory use".
The command is not recognized on Sierra V.32bis or earlier modems.
Compatibility: - - - - - S - - - |
|
| &F1 |
On Telebit modems, "&F1" loads the factory defaults considered suitable
for asynchronous Front End Processor (FEP host ports, operating at a fixed
9600bps speed. (Settings shown are from the Telebit 3000/Worldblazer)
B1 E0 L2 M1 P Q2 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q0 &R2 &S4 &T4 &X0 S0=1 S1=0 S2=255 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F2 |
On USR/3Com modems, the "&F2" command sets the "Software flow control
template" factory defaults. No other information was provided.
Compatibility: - - - - U - - - - |
|
| &F2 |
On Telebit Modems, "&F2" selects "Intelligent Answer Mode". This configuration
is geared towards applications that know how to interpret result codes.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q2 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q0 &R2 &S4 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F3 |
On Sierra V.32bis modems, the "&F3" command sets the following factory
defaults, which are identical to those generated by the &F0 command:
B1, E1, L2, M1, N1, P, Q0, V1, W0, X4, Y0, &C1, &D0, &G0, &J0, &K3, &L0, &P0, &Q5, &R0, &S0, &T4, &U0, &X0, &Y0, \C0, \G0, \N6, \Q3, \T000, \V1, \X0, %A000, %D1, S0=0, S2=43, S3=13, S4=10, S5=8, S6=2, S7=40, S8=2, S9=6, S10=14, S11=75, S12=40, S14=0xAA, S16=0x00, S18=0, S21=0x20, S22=0x76, S23=0x07, S25=5, S26=1, S27=0x49, S36=7, S37=0, S38=20, S46=138, S48=7, S49=10, S50=200, S63=0, S82=128.There are also undocumented registers that are set to factory defaults. Compatibility: - - - - - S - - - |
|
| &F3 |
On Telebit Modems, "&F3" loads a configuration suited for use with
System V HoneyDanBer (HDB) UUCP coounications. For more efficient PEP
transmissions, each modem will emulate the handshake the UUCP protocol,
with the local modem acknowledging receipt of packets on behalf of the
remote system.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q2 V1 X0 Y0 &C1 &D3 &G0 &J0 &L0 &Q0 &R3 &S4 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=2 S59=0 S60=0 S61=0 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=30 S112=1 S180=3 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F4 |
On Telebit Modems, "&F4" loads a configuration suited for use with
BSD UUCP 4.2 or 4.3, as well as SCO XENIX. This is generally compatible
with systems using a Version 2 UUCP protocol. For more efficient PEP
transmissions, each modem will emulate the handshake the UUCP protocol,
with the local modem acknowledging receipt of packets on behalf of the
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q2 V1 X0 Y0 &C1 &D3 &G0 &J0 &L0 &Q0 &R3 &S1 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=254 S56=17 S57=19 S58=0 S59=0 S60=0 S61=0 S62=15 S63=0 S64=1 S68=3 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=30 S112=1 S180=3 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F5 |
On Telebit Modems, "&F5" loads a configuration for transparent synchronous
operations and typically used with synchronous terminals or devices.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q1 V1 X0 Y0 &C1 &D2 &G0 &J0 &L0 &Q6 &R3 &S3 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=0 S181=0 S183=25 S190=1 S252=0 S253=0 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F8 |
On Telebit Modems, "&F8" loads a configuration compatible with IBM PC/MAC
software flow control (XON/XOFF).
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q1 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q6 &R3 &S0 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F9 |
On Telebit Modems, "&F9" loads a configuration compatible with IBM PC/MAC
hardware flow control (RTS/CTS). For typical PPP transmissions, this
profile is a good starting configuration.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q0 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q0 &R3 &S0 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=2 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F10 |
On Telebit Modems, "&F10" loads a configuration for leased line operation
where this modem will be set to asynchronous originate mode.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E0 L2 M1 P Q2 V1 X1 Y0 &C1 &D0 &G0 &J0 &L1 &Q0 &R3 &S1 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=255 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=5 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=0 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F11 |
On Telebit Modems, "&F11" loads a configuration for leased line operation
where this modem will be set to asynchronous answer mode.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E0 L2 M1 P Q2 V1 X1 Y0 &C1 &D0 &G0 &J0 &L1 &Q0 &R3 &S1 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=255 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=5 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=0 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=2 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F12 |
For Telebit Modems, "&F12" loads a configuration for leased line operation
where this modem will be set to synchronous originate mode.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E0 L2 M1 P Q2 V1 X1 Y0 &C1 &D0 &G0 &J0 &L1 &Q0 &R3 &S1 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=255 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=5 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=0 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=0 S181=0 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F13 |
For Telebit Modems, "&F13" loads a configuration for leased line operation
where this modem will be set to synchronous answer mode.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q2 V1 X1 Y0 &C1 &D0 &G0 &J0 &L1 &Q6 &R3 &S3 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=255 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=5 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=0 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=0 S181=0 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F32 |
For Telebit Modems, "&F32" loads a configuration that allows the modem to
operate in asynchronous mode when idle, and switches to synchronous mode
when a connection to a remote modem is established.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q2 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q1 &R3 &S3 &T4 &X0 S0=1 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=255 S112=1 S180=0 S181=0 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F33 |
For Telebit Modems, "&F33" loads a configuration that is compatible with a
HP3000 system that uses ENQ/ACK flow control and this modem is connected
to the host. (Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q0 V1 X1 Y0 &C1 &D2 &G0 &J0 &L0 &Q0 &R2 &S1 &T4 &X0 S0=1 S1=0 S2=255 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=7 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=1 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=40 S112=1 S180=3 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
| &F34 |
For Telebit Modems, "&F34" loads a configuration that is compatible with a
HP3000 system that uses ENQ/ACK flow control and this modem is connected to
a terminal.
(Settings shown are from the Telebit 3000/Worldblazer)
B1 E1 L2 M1 P Q0 V1 X1 Y0 &C1 &D0 &G0 &J0 &L0 &Q0 &R3 &S0 &T4 &X0 S0=0 S1=0 S2=43 S3=13 S4=10 S5=8 S6=2 S7=40 S8=2 S09=6 S10=14 S11=70 S12=50 S18=0 S25=5 S26=1 S38=0 S41=0 S45=0 S47=4 S48=0 S50=0 S51=255 S56=17 S57=19 S58=3 S59=0 S60=0 S61=1 S62=15 S63=0 S64=0 S68=255 S69=0 S90=0 S93=8 S94=1 S100=0 S102=0 S104=0 S105=1 S111=41 S112=1 S180=3 S181=1 S183=25 S190=1 S252=0 S253=10 S254=255 S255=255 Compatibility: - - - - - - - T - |
|
|
&G
(Guard Tones) |
The Guard Tone is used with FSK, PSK or DPSK transmission systems.
It causes the modem to generate a tone at 550Hz or 1800Hz. It's purpose
is to prevent certain telephone switching systems from becoming confused
by the modem carrier and prevents calls from being terminated prematurely.
When a guard tone is not used, the "B" command must be set to the CCITT/ITU operation mode ("B0"). Standards: The "&G" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems. See individual option descriptions. Note: On Sierra modems, the "&G" command only exists on V.32bis models and earlier designs. |
|
| Modifiers | Description | |
| &G0
(Default) |
No Guard tone is generated. This is the correct setting for use in
North America (United States, Canada and Mexico).
Compatibility: 2 4 - R U S L T C Note: On Rockwell "W-Class" modems, "&G2" is the default setting. |
|
| &G1 |
The answering modem will generate a 550Hz guard tone, which is used in
some European countries (not the U.K.).
Compatibility: 2 4 - - U S - T C Note: Although Lucent doesn't document anything other than "&G0", their modems probably really do support guard tones in modem models sold in countries that require guard tone operation. Note: Some European countries also require that the ITU V.25 mode be selected by issuing "B0" command. |
|
| &G1 |
On Rockwell modems, the "&G1" command disables the guard tone although "&G0"
should be used to disable guard tone in a portable fashion.
Compatibility: - - - R - - - - - Note: Some European countries also require that the ITU V.25 mode be selected by issuing "B0" command. |
|
| &G2
(Default) |
The answering modem will generate a 1800Hz guard tone, which is used in
the United Kingdom.
Compatibility: 2 4 - R U S - T C Note: Although Lucent doesn't document anything other than "&G0", their modems probably really do support guard tones in modem models sold in countries that require guard tone operation. On Rockwell "W-Class" models, "&G2" is the default. Some European countries also require that the ITU V.25 mode be selected by issuing "B0" command. |
|
|
&H
(Set Transmit to DTE flow control) |
On USR/3Com modems, this command controls what type of flow control is to
be performed between the modem and the DTE.
Standards: The "&H" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
| Modifiers | Description | |
| &H0 | The modem sends data to the DTE when it is available. All flow control is disabled. | |
| &H1
(Default) |
Hardware Flow Control is to be implemented by monitoring the Clear to Send (CTS) signal from the DTE. When CTS is false, the modem will not transmit data to the DTE. | |
| &H2 | Software flow control is used when sending data to the DTE. The modem will transmit data to the DTE until the ASCII character X-OFF is received from the DTE. Transmissions may resume when the an X-ON character is received from the DTE. | |
| &H3 | Hardware and Software flow control are used when sending data to the DTE. Refer to the description of "&I1" and "&I2" for how the two types of flow control work. Also see the USR/3Com "&I" and "&R" commands for managing flow control from the DTE to the modem. | |
|
&H
(Set Speed Negotiation Mode) |
On Sierra V.34 modems, the "&H" command controls the selection of the
modulation protocols that may be negotiated with the remote modem. If a
specific set of protocols are required and a common protocol cannot be
negotiated, the call will fail.
When an external clock is used (see "&X1" command), a fixed modulation protocol should be selected. Standards: The "&H" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - - S - - - Note: The &H command does not exist on Sierra V.32bis and earlier modems. |
|
| Modifiers | Description | |
| &H0
(Default) |
Automatic mode. Any speed can be negotiated with the remote modem. | |
| &H1 | Negotiate V.34 speeds only (4,800 to 33,600bps). | |
| &H2 | Negotiate up to V.32bis speeds (300 to 14,400bps). | |
| &H3 | Negotiate V.32bis speeds only (4,800 to 14,400bps). | |
| &H4 | Negotiate up to V.32 speeds (300 to 9,600bps). | |
| &H5 | Negotiate V.32 speeds only (4,800 to 9,600bps). | |
| &H6 | Negotiate V.22bis speeds only (1,200 to 2,400bps). | |
| &H7 | Negotiate V.22 speeds only (1,200bps). | |
| &H8 | Negotiate Bell 212 only (1,200bps). | |
| &H9 | Negotiate Bell 103 only (300bps). | |
| &H10 | Negotiate Bell V.21 only (300bps). | |
|
&I
(Receive Data Software Flow Control) |
This command interacts with the "&R" command on certain modem brands to
specify how software flow control is to behave.
Standards: The "&I" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
| Modifiers | Description | |
| &I0
(Default) |
Software Flow control is disabled. Any XON/XOFF characters sent by the DTE or received from the remote modem pass through the modem without any action. This setting is required in PPP or SLIP applications. Hardware Flow control should be used instead. | |
| &I1 | The local modem responds to XON/XOFF signals received from the DTE, and sends the XON/XOFF to the remote modem. | |
| &I2 | The local modem responds to XON/XOFF signals received from the DTE, but does not send the XON/XOFF to the remote modem. | |
|
&J
(Jack Selection) |
This command controls how the telco leads are utilized by certain specialized
modems, mainly those that also support a leased-line configuration.
Standards: The "&J" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or have the same function. See individual option descriptions. |
|
| Modifiers | Description | |
| &J0
(Default) |
The Auxillary CPE telco leads are disabled.
Compatibility: - - - - - - L T C Note: Rockwell and Lucent modems accept this command but take no action. |
|
| &J1 |
The A/A1 control function is selected.
Compatibility: - - - - - - - T C Note: Rockwell modems accept this command but take no action. |
|
| &J2 |
The MI/MIC control is selected.
Compatibility: - - - - - - - T - |
|
|
&K
(DTE Port Flow Control) |
The "&K" commands provide a variety of methods to implement flow
control between the modem and the DTE. Note that some Modifier values
are not used.
Standards: The "&K" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or have the same function. See individual option descriptions. Note: Most of the modem makers have compatible flow control options, but USR/3Com modems use a completely different set of commands to provide the same functionality. |
|
| Modifiers | Description | |
| &K0
(Default) |
DTE flow control is disabled.
Compatibility: - 4 - R - S L - - Note: On Rockwell modems, "&K6" is the default setting. For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &K3 |
Bi-directional hardware flow control is used. The modem uses the
CTS line to regulate data coming from the DTE. The DTE uses the
RTS line to control data coming from the modem. This is the preferred
setting for PPP/SLIP connections.
Compatibility: - 4 - R - S L - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &K4 |
Bi-directional software flow control is used. XOFF characters received
from the DTE cause the modem to suspend transmissions to the DTE. An XON
resumes transmissions to the DTE. The modem also sends XOFF/XON characters
to the DTE to regulate characters being sent to the modem. Software flow
control should not be used with PPP/SLIP protocols.
Compatibility: - 4 - R - S L - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &K5 |
Bi-directional transparent software flow control is used. This mode is
used by Hayes Smartcom III communication software that allows software
flow control to be used and still allows XON/XOFF characters in binary
data to be not be interpreted by the modem.
Compatibility: - 4 - R - S - - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &K6
(Default) |
On Rockwell modems, enables both RTS/CTS and XON/XOFF flow control.
Compatibility: - - - R - - - - - |
|
|
&K
(Enable/Disable Data Compression) |
On USR/3Com modems, "&K" is used to specify what types of data compression
are to be negotiated with the remote modem.
Standards: The "&K" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: This description is valid only for USR/3Com modems. Other brands that have a "&K" command use it for an unrelated function, described above. |
|
| Modifiers | Description | |
| &K0 | Data Compression is disabled. | |
| &K1
(Default) |
The modem is allowed to negotiate the best compression method both modems support. | |
| &K2 | Data Compression must be used. If compression cannot be negotiated, the call will fail to negotiate. | |
| &K3 | The modem will only negotiate LAP-M/V.42bis/V.44 compression. MNP-5 will not be used even if that is the only compression method that the remote modem is willing to negotiate. | |
|
&L
(Line Selection) |
The "&L" command instructs the modem as to whether a leased line or a PSTN
(dial-up) line is to be used.
In leased line/direct connect modes, most modems automatically establish and maintain carrier. If carrier is interrupted, the modem will re-establish carrier without DTE intervention. Some modems support only a limited set of speeds in leased line configurations. Standards: The "&L" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or have the same function. See individual option descriptions. |
|
| Modifiers | Description | |
| &L0
(Default) |
The modem is connected to the Public Switched Telephone Network (PSTN)
via an analog or digital link.
Compatibility: 2 4 - R - S L T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &L1 |
The modem is connected to a leased line.
Compatibility: 2 4 - R - S L T - Note: Lucent and Rockwell modems accept this command but treat it the same as the "&L0" command. For Sierra modems, this command only exists on V.32bis models and earlier designs. Some modems only allow specific speeds to be used in leased line mode. |
|
|
&M
(Asynchronous or Synchronous Mode) |
The "&M" commands are used to specify if the modem communicates with the
DTE using asynchronous or synchronous communications. Some related
operations are controlled by the "&Q" command.
Standards: The "&M" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or have the same function. See individual option descriptions. Internal modems may not support Synchronous modes but the commands may be accepted. The S25 register may also interact with the &M commands. |
|
| Modifiers | Description | |
| &M0
(Default) |
Asynchronous Mode, also known as Direct Mode. All serial transmissions to
and from the DTE use Start and Ttop bits. ("&M0" is equivalent to "&Q0".)
Compatibility: - 4 - R - S L T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &M1 |
Synchronous Mode 1. The modem communicates asynchronously with the DTE
in Command mode. After DCD transitions from FALSE to TRUE or the CONNECT
message is sent to the DTE, subsequent transmissions to and from the
DTE are in synchronous mode. There may be additional delays or criteria
that may occur that effect when communication in synchronous mode begins, so
you should refer to the documentation for the specific modem.
("&M1" is equivalent to "&Q1".)
Compatibility: - 4 - R - S - T - Note: For Sierra modems, this description only applies to V.32bis models and earlier designs. |
|
| &M1 |
Sierra V.34 modems document the "&M1" command as being for factory use only
and provide no other information.
Compatibility: - - - - S - - - - |
|
| &M2 |
Synchronous Mode 2. The modem communicates synchronously at all
times. Modems dial a stored telephone number automatically when DTR goes
from FALSE to TRUE. This modem is to be used with synchronous terminals.
("&M2" is equivalent to "&Q2".)
Compatibility: - 4 - R S - - T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &M3 |
Synchronous Mode 3. The modem communicates synchronously at all
times. The modem begins transmissions when DTR goes from FALSE to TRUE.
A handset is used to manually originate the synchronous call.
("&M3" is equivalent to "&Q3".)
Compatibility: - 4 - R S - - T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
|
&M
(Select Error Control) |
On USR/3Com modems, the "&M" commands specify error control.
Standards: The "&M" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: Other manufacturers use the "&M" command for unrelated functions. |
|
| Modifiers | Description | |
| &M0 | Error Control is disabled. This setting is not recommended. | |
| &M1 | USR/3Com documents this command as reserved. | |
| &M2 | USR/3Com documents this command as reserved. | |
| &M3 | USR/3Com documents this command as reserved. | |
| &M4
(Default) |
Normal/ARQ Error Control on 1200bps and higher speeds. | |
| &M5 | ARQ-only Mode | |
|
&N
(Set Special Echo Canceller Training Sequence) |
Sierra Semiconductor V.32bis modems use this command to control Echo
Cancellation. (No additional description information was available.)
Standards: The "&N" command is not part of the EIA/TIA-602 standard. Compatibility: - 4 - - - S - - - Note: USR/3Com modems use the "&N" command for unrelated functions. |
|
| Modifiers | Description | |
| &N0 | Special Echo Canceller Training Sequence is not required. | |
| &N1
(Default) |
Special Echo Canceller Training Sequence required. | |
|
&N
(Set Connect Speed) |
USR/3Com modems use this command to force a specific carrier
speed that is to be used during a data connection. If that
exact speed cannot be established, the modem will go on-hook.
Use of this command is not recommended since it will abort
data calls or prevent data calls from being establihed due to
changes in line impairments.
Standards: The "&N" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: Sierra modems use the "&N" command for unrelated functions. |
|
| Modifiers | Description | |
| &N0
(Default) |
The modem is allowed to select the best carrier rate that the line conditions allow with an acceptable number of bit errors per second. This is the recommended setting. | |
| &N1 | The modem is allowed to connect only at 300bps. | |
| &N2 | The modem is allowed to connect only at 1200bps. | |
| &N3 | The modem is allowed to connect only at 2400bps. | |
| &N4 | The modem is allowed to connect only at 4800bps. | |
| &N5 | The modem is allowed to connect only at 7200bps. | |
| &N6 | The modem is allowed to connect only at 9600bps. | |
| &N7 | The modem is allowed to connect only at 12,000bps. | |
| &N8 | The modem is allowed to connect only at 14,400bps. | |
| &N9 | The modem is allowed to connect only at 16,800bps. | |
| &N10 | The modem is allowed to connect only at 19,200bps. | |
| &N11 | The modem is allowed to connect only at 21,600bps. | |
| &N12 | The modem is allowed to connect only at 24,000bps. | |
| &N13 | The modem is allowed to connect only at 26,400bps. | |
| &N14 | The modem is allowed to connect only at 28,800bps. | |
| &N15 | The modem is allowed to connect only at 31,200bps. | |
| &N16 | The modem is allowed to connect only at 33,600bps. | |
| &N17 | The modem is allowed to connect at PCM speeds. | |
|
&P
(Sets Pulse Dialing Make/Break ratio) |
The "&P" command controls the duty cycle of the "make" and "break" pulses
used when using pulse dialing (also known as rotary dialing).
While most countries use a 39% make 61% break ratios, the United
Kingdom and Hong Kong use a 33% make 67% break ratios. Using the
wrong make/break ratio will usually cause pulse dialing to fail or
dial incorrect numbers.
Standards: The "&P" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: Pulse dialing is typically fixed at 10 digit pulses per second. However, some telephone company switching equipment allows higher rates. Some Rockwell modems allow faster pulse dialing via the &P2 and &P3 commands. This faster dialing is not widely supported by the telephone companies, and this feature should be considered non-portable. |
|
| Modifiers | Description | |
| &P0
(Default) |
The pulse dialing make/break ratio is set to 39%/61%. This
is the correct setting for North America.
Compatibility: 2 4 - R U S L - C Note: Lucent modems vary from others, generating a 36%/64% ratio. For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &P1 |
The pulse dialing make/break ratio is set to 33%/67%. This
is the correct setting for the United Kingdom and Hong Kong.
Compatibility: 2 4 - R U S L - C Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &P2 |
On Rockwell modems, the "&P2" command sets the pulse dialing make/break ratio
to 39%/61%, which is the correct ratio for North America. "&P2" also
increases the pulse rate to 20 pulses per second, which is not compatible
with most telephone switching systems. ("&P0" and "&P1" use 10 pulses per
second.)
Compatibility: - - - R - - - - - |
|
| &P3 |
On Rockwell modems, the "&P3" command sets the pulse dialing make/break ratio
to 33%/67%, which is the correct ratio for Hong Kong and the United Kingdom.
"&P3" also increases the pulse rate to 20 pulses per second, which is not
compatible with most telephone switching systems. ("&P0" and "&P1"
use 10 pulses per second.)
Compatibility: - - - R - - - - - |
|
|
&Q
(Asynchronous or Synchronous Operation) |
The "&Q" commands are used to specify if the modem communicates with the
DTE using asynchronous or synchronous communications. Some related
operations are controlled by the "&M" command.
Standards: The "&Q" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or have the same function. See individual option descriptions. |
|
| Modifiers | Description | |
| &Q0 |
Asynchronous operation. (This must be set for V.23 connections.)
("&Q0" is equivalent to "&M0".) Compatibility: - 4 - R - S L T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. On Lucent modems, this command is equivalent to the "\N1" command. |
|
| &Q1 |
Synchronous Mode 1. The modem communicates asynchronously with the DTE
in Command mode. After DCD transitions from FALSE to TRUE or the CONNECT
message is sent to the DTE, subsequent transmissions to and from the
DTE are in synchronous mode. There may be additional delays or criteria
that may occur that effect when communication in synchronous mode begins, so
you should refer to the documentation for the specific modem.
("&Q1" is equivalent to "&M1".) Compatibility: - 4 - R - S - T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &Q2 |
Synchronous Mode 2. The modem communicates synchronously at all
times. Modems dial a stored telephone number automatically when DTR goes
from FALSE to TRUE. This modem is to be used with synchronous terminals.
("&Q2" is equivalent to "&M2".) Compatibility: - 4 - R - S - T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &Q3 |
Synchronous Mode 3. The modem communicates synchronously at all
times. The modem begins transmissions when DTR goes from FALSE to TRUE.
A handset is used to manually originate the synchronous call.
("&Q3" is equivalent to "&M3".) Compatibility: - 4 - R - S - T - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &Q4 |
The "&Q4" command enabled AutoSync mode. When used in conjunction with
the Hayes Synchronous Interface (HSI) capability in the DTE, it provides
synchronous communication from an asynchronous terminal.
Synchronous Mode 3. This command interacts with the "S19", "S20",
and "S25".
Compatibility: - 4 - R - S - - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &Q5
(Default) |
The modem should make data connections using V.42 or MNP-2 through MNP-4
error-correction (synchronous line transmission modes).
Compatibility: - 4 - R - S L - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. On Lucent modems, this command is equivalent to the "\N3" command. |
|
| &Q6 |
The "&Q6" command forces data connections to use standard buffered Data Mode.
Compatibility: - 4 - R - S L - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. On Lucent modems, this command is equivalent to the "\N0" command. |
|
| &Q6 |
On Telebit modems, the "&Q6" command enables transparent synchronous mode.
Register "S253" controls Command Mode operations.
Compatibility: - - - - - - - T - Note: All other modems with a "&Q6" command perform a different action. See above. | |
|
&R
(Clear to Send) |
The Clear To Send (CTS) signal is controlled by the "&R" command.
Standards: The "&R" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: USR/3Com Modems use the "&R" command for unrelated operations. |
|
| Modifiers | Description | |
| &R0
(Default) |
The CTS signal generated by the modem follows the RTS signal
received from the DTE. The signal is delayed by the time specified
by Register "S26".
Compatibility: - 4 - R - S - T - Note: For Sierra modems, this description applies to V.34 modems only. The Sierra V.32bis command description is below. |
|
| &R0 |
In Sierra modems operating in asynchronous mode, CTS is TRUE when the modem
is in Command Mode.
In synchronous mode, when RTS goes TRUE, CTS will go TRUE after a delay. Compatibility: - - - - - S - - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &R1 |
When the modem is in Data Mode (when the CONNECT message is
sent to the DTE), CTS is TRUE.
Compatibility: - 4 - R - S - T - Note: For Sierra modems, this description applies to V.34 modems only. The Sierra V.32bis command description is below. |
|
| &R1
(Default) |
In Sierra modems, "&R1" command selects CTS behavior as follows:
In asynchronous Data Mode, CTS is forced off.
In asynchronous Data Mode, CTS follows RTS. In Command Mode, CTS is forced on. Compatibility: - - - - - S - - - Note: For Sierra modems, this command only exists on V.32bis models and earlier designs. |
|
| &R2 |
When in Data Mode, the CTS signal follows the RTS signal. CTS follows
RTS by 200msec. When in Command Mode, CTS is FALSE.
Compatibility: - 4 - - - S - T - Note: On Sierra modems, this command only exists on V.32bis and earlier commands. modems. |
|
| &R3 |
In Telebit modems, "&R3" forces CTS to always be TRUE when hardware flow
control is disabled. Otherwise, CTS will control hardware flow control.
Compatibility: - - - - - S - T - |
|
| &R3 |
In Sierra modems, the "&R3" command causes the CTS signal to be forced on.
Compatibility: - - - - - S - - - |
|
| &R4 |
In Telebit modems when "&R4" is used and a data connection is in progress,
the CTS signal follows the RTS signal, after the delay specified by the
S26 register. When the modem is in Command Mode, CTS follows DTR.
Compatibility: - - - - - - - T - |
|
|
&R
(Set Receive Data from DTE flow control) |
On USR/3Com modems, the Request to Send (RTS) signal is controlled by the
"&R" command.
Standards: The "&R" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: All other manufacturers use the "&R" command for unrelated functions. |
|
| Modifiers | Description | |
| &R0 | USR/3Com documents this command as reserved. | |
| &R1 | On USR/3Com modem, the "&R1" command causes the modem to ignore any transition on the RTS signal from the DTE. | |
| &R2
(Default) |
On USR/3Com modems, the "&R2" specifies that data is only transmitted to the DTE when the RTS signal from the DTE is true. | |
|
&S
(Data Set Ready) |
The DTE DSR signal is controlled by the "&S" Commands.
Standards: The "&S" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. |
|
| Modifiers | Description | |
| &S0
(Default) |
The DSR line is TRUE at all times.
Compatibility: - 4 - R U S L T C |
|
| &S1 |
The DSR signal goes TRUE after the modem detects an answer tone
and remains on until the call ends.
Compatibility: - 4 - R U S - T C |
|
| &S2 |
DSR signal remains TRUE except when a call disconnects. On disconnect
the DSR signal goes FALSE for the amount of time specified by the S47
register, then goes TRUE again.
Compatibility: - - - - - - - T - |
|
| &S2 |
DSR is TRUE when carrier is being detected on the telephone loop.
Compatibility: - - - - - S - - - |
|
| &S3 |
DSR is TRUE if DTR is TRUE or carrier is detected and DTR is true.
DSR goes FALSE if DTR goes FALSE or carrier is lost.
Compatibility: - - - - - - - T - |
|
| &S3 |
DSR is TRUE at all times.
Compatibility: - - - - - S - - - |
|
| &S4 |
DSR is TRUE only when carrier is detected from the remote modem.
Compatibility: - - - - - - - T - |
|
|
&T
(Test Commands) |
The "&T" commands are used to perform a variety of diagnostic tests.
Standards: The "&T" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: The commands related to Digital Loopback Tests ("&T3", "&T4", "&T5", "&T6" and "&T7") are not available on all modem models. |
|
| Modifiers | Description | |
| &T0
(Default) |
Any test that is in progress is terminated. When the modem is started
or is not performing the a test, this is the default state.
Compatibility: 2 4 - R U S L T C Note: Both "&T0" and "&T5" are defaults at the same time since they control separate operations. In all other cases, a given "AT" command only has one default setting. |
|
| &T1 |
The modem performs an Analog Loopback test.
Compatibility: 2 4 - R U S L T C |
|
| &T3 |
The modem performs a Digital Loopback test.
Compatibility: 2 4 - R U S - T C |
|
| &T4 |
Instructs the local modem to accept a request from a remote modem
for a Digital Loopback Test. Typically, the called modem would execute
a "&T4" command, then the calling modem would execute a "&T6" or "&T7"
command.
Compatibility: 2 4 - R U S - T C |
|
| &T5
(Default) |
Instructs the local modem to refuse any request from a remote modem
to participate in a Digital Loopback Test. By default, a modem refuses a
request for a Digital Loopback Test that comes from a remote modem, and
this capability must be enabled
Compatibility: 2 4 - R U S - T C Note: Both "&T5" and "&T0" are defaults at the same time since they control separate operations. In all other cases, a given "AT" command only has one default setting. |
|
| &T6 |
The local modem performs a Remote Digital Loopback Test, assuming the
remote modem accepts the Digital Loopback Test.
Compatibility: 2 4 - R U S L T C |
|
| &T7 |
The local modem performs a Remote Digital Loopback Test, assuming the
remote modem accepts the Digital Loopback Test. The local modem also
performs a self-test.
Compatibility: 2 4 - R U S - T C |
|
| &T8 |
The modem performs an Analog Loopback test and a self-test.
Compatibility: 2 4 - R U S - T C |
|
| &T9 |
On Sierra V.34 modems, the "&T9" command forces a Self-Test to terminate.
Compatibility: - - - - - S - - - Note: The "&T9" command is not present on V.32bis and earlier Sierra modems. |
|
| &T9 |
On Telebit modems, the "&T9" command forces a Self-Test to terminate and
the internal diagnostics that are performed on a power-up are executed.
The results of those tests are available via the "I1" command. This
command essentially resets the modem, returning all settings to those
stored in non-volatile memory.
Compatibility: - - - - - - - T - |
|
|
&U
(Trellis Coding) |
The "&U" command controls whether Trellis coding is used with V.32
transmissions (9600bps).
Standards: The "&U" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: USR/3Com modems use the "&U" command for unrelated operations. |
|
| &U0
(Default) |
Trellis Coding will be used for V.32 transmissions.
Compatibility: - 4 - R - S - - C |
|
| &U1 |
Trellis Coding will not be used for V.32 transmissions. QAM will be used.
Compatibility: - 4 - R - S - - C |
|
|
&U
(Set Speed Floor) |
On USR/3Com modems running at 28,800bps or higher, the "&U" command
specifies that the carrier speed must be at least the value speed or
the call will disconnect.
Standards: The "&U" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - Note: Other modems that have a "&U" command use it for unrelated operations. |
|
| &U0
(Default) |
No minimum carrier speed is specified. | |
| &U1 | The minimum carrier speed is 300bps. | |
| &U2 | The minimum carrier speed is 1200bps. | |
| &U3 | The minimum carrier speed is 2400bps. | |
| &U4 | The minimum carrier speed is 4800bps. | |
| &U5 | The minimum carrier speed is 7200bps. | |
| &U6 | The minimum carrier speed is 9600bps. | |
| &U7 | The minimum carrier speed is 12,000bps. | |
| &U8 | The minimum carrier speed is 14,400bps. | |
| &U9 | The minimum carrier speed is 16,800bps. | |
| &U10 | The minimum carrier speed is 19,200bps. | |
| &U11 | The minimum carrier speed is 21,600bps. | |
| &U12 | The minimum carrier speed is 24,000bps. | |
| &U13 | The minimum carrier speed is 26,400bps. | |
| &U14 | The minimum carrier speed is 28,800bps. | |
| &U15 | The minimum carrier speed is 31,200bps. | |
| &U16 | The minimum carrier speed is 33,600bps. | |
|
&V
(View Active Configuration) |
The "&V" command displays most or all command and S register settings that
are active in the modem, as well as the settings that are stored profiles,
including any stored telephone numbers.
Standards: The "&V" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. Note: USR/3Com modems use the I4 command to provide this functionality. |
|
| &V0 |
Displays the contents of the active and stored profile #0 (A).
Compatibility: - 4 - R - S L T C Note: On Sierra modems, the "V0" command displays all stored profiles and all stored telephone numbers. |
|
| &V1 |
Displays the contents of stored profile #1 (B).
Compatibility: - - - - - - - - C |
|
|
&W
(Stored Active Configuration) |
The "&W" command stores the current or active configuration (also known as the
"profile") of the modem into non-volatile memory in the modem. When the modem
is reset, the factory configuration is loaded, and then the stored
configuration is loaded prior to the modem responding to commands.
Depending on the modem, the "&W" command may store all settings or only a portion of all possible modem parameters. Most consumer-grade modems only store a portion of all paremeters in non-volatile RAM. Parameters not stored will revert to their factory settings after a modem reset occurs. So-called "Soft" or "Win" modems typically emulate the "&W" command by storing configuration parameters in a file or other data structure managed by the operating system running on the host computer. Standards: The "&W" command is not part of the EIA/TIA-602 standard. Compatibility: Not all options are implemented in all modems or behave in the same ways. See individual option descriptions. |
|
| &W0 |
The "&W0" command will save the active configuration in stored profile #0
(or "A").
Compatibility: 2 4 - R U S L T C Note: On Telebit modems, the configuration is written to "A" or "B" based on the setting of register "S255". If "S255==0", the configuration is stored in "A". If "S255==1", the configuration is stored in "B". If "S255=255", the setting of the front panel A/B switch will determine where the configuration is stored. |
|
| &W1 |
The "&W1" command will save the active configuration in stored profile #1
(or "B").
Compatibility: - 4 - R U S - T C |
|
|
&X
(Select Clock Source) |
When the modem is operating in synchronous mode, the "&X" command selects
which clock will be used by the modem transmitter.
Standards: The "&U" command is not part of the EIA/TIA-602 standard. Compatibility: - 4 - R - S - T - Note: On Sierra modems, the "&X" command exists on V.32bis models and earlier designs. |
|
| &X0
(Default) |
The transmit clock signal is generated by the local modem. The clock signal is also transmitted on pin 15 for the RS-232 DB25 connector. | |
| &X1 | The DTE device is responsible for providing the clock signal to the modem. The modem receives the DTE clock on pin 24 of the RS-232 DB25 connector. | |
| &X2 | The modem accepts clock from the remote modem. The received clock is also sent to the DTE on pin 15 of the RS-232 DB25 connector. | |
|
&Y
(Select Stored Profile) |
When the modem resets or is power-cycled, the "&Y" command
specifies which user-stored profile should be loaded after the factory
settings are loaded.
Standards: The "&Y" command is not part of the EIA/TIA-602 standard. Compatibility: - 4 - R - S - - C Note: USR/3Com modems use the "&Y" command for unrelated operations. |
|
| &Y0 | The modem will use stored profile #0 (or "A") on reset. | |
| &Y1 | The modem will use stored profile #1 (or "B") on reset. | |
|
&Y
(Sets break handling) |
On USR/3Com modems, when a break signal (spacing) is received from the DTE,
the "&Y" command specifies how the modem will respond.
Standards: The "&Y" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
| &Y0 | On receipt of a data break from the DTE, all untransmitted characters held by the modem are discarded. A data break is not transmitted to the remote modem. | |
| &Y1
(Default) |
On receipt of a data break from the DTE, all untransmitted characters held by the modem are discarded. A data break is immediately transmitted to the remote modem. | |
| &Y2 | On receipt of a data break from the DTE, a data break is transmitted to the remote modem ahead of any untransmitted characters held by the modem. After sending the data break, transmission of characters continue. | |
| &Y3 | USR/3Com documents this command as reserved. | |
|
&Zn=s
(Store telephone number in non-volatile memory) |
This command stores string s in one of four areas in non-volatile
RAM. N is a value from 0 to 3. The maximum number of digits
and modifiers that can be stored varies by modem but is usually at least
30 characters.
Standards: The "&Zn=s" command is not part of the EIA/TIA-602 standard. Compatibility: - 4 - R U S L - C |
|
|
&Zn=L
(Stores the last dialed telephone number in non-volatile memory) |
This command stores the last dialed telephone number string.
Standards: The "&Zn=L" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
|
&Zn?
(Display stored telephone numbers in non-volatile memory) |
On USR/3Com modems, the &Zn? command displays the dialing string stored in
one of four areas in non-volatile RAM. N is a value from 0 to 3.
Standards: The "&Zn?" command is not part of the EIA/TIA-602 standard. Compatibility: - - - - U - - - - |
|
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