Basic Modem AT Command Set

Some applications may require a custom modem initialisation string. The AT Command set listed below is for reference only.

Basic AT Commands

A/         Re-execute command
A          Go off-hook and attempt to answer a call
B0         Select V.22 connection at 1200 bps
B1         Select Bell 212A connection at 1200 bps
C1         Return OK message
Dn         Dial modifier
E0         Turn off command echo
E1         Turn on command echo
F0         Select auto-detect mode (equivalent to N1). (RC144)
F1         Select V.21 or Bell 103. (RC144)
F2         Reserved. (RC144)
F3         Select V.23 line modulation. (RC144)
F4         Select V.22 or Bell 212A 1200 bps line speed. (RC144)
F5         Select V.22 bis line modulation. (RC144)
F6         Select V.32 bis or V.32 4800 line modulation. (RC144)
F7         Select V.32 bis 7200 line modulation. (RC144)
F8         Select V.32 bis or V.32 9600 line modulation. (RC144)
F9         Select V.32 bis 12000 line modulation. (RC144)
F10        Select V.32 bis 14400 line modulation. (RC144)
H0         Initiate a hang-up sequence
H1         If on-hook, go off-hook and enter command mode
I0         Report product code
I1         Report pre-computed checksum
I2         Report OK
I3         Report firmware revision, model, and interface type
I4         Report response programmed by an OEM
I5         Report the country code parameter
I6         Report modem data pump model and code revision
I7         Reports the DAA code (W-class models only)
L0         Set low speaker volume
L1         Set low speaker volume
L2         Set medium speaker volume
L3         Set high speaker volume
M0         Turn speaker off
M1         Turn speaker on during handshaking and turn speaker off while receiving carrier
M2         Turn speaker on during handshaking and while receiving carrier
M3         Turn speaker off during dialling/receiving carrier and turn speaker on during answering
N0         Turn off automode detection
N1         Turn on automode detection
O0         Go on-line
P          Force pulse dialling
Q0         Allow result codes to DTE
Q1         Inhibit result codes to DTE
Sn         Select S-Register as default
Sn?         Return the value of S-Register n
=v         Set default S-Register to value v
?          Return the value of default S-Register
T          Force DTMF dialling
V0         Report short form (terse) result codes
V1         Report long form (verbose) result codes
W0         Report DTE speed in EC mode
W1         Report line speed, EC protocol and DTE speed
W2         Report DCE speed in EC mode
X0         Report basic call progress result codes
X1         Report basic call progress result codes and connections speeds
X2         Report basic call progress result codes and connections speeds
X3         Report basic call progress result codes and connection rate
X4         Report all call progress result codes and connection rate
Y0         Disable long space disconnect before on-hook
Y1         Enable long space disconnect before on-hook
Z0         Restore stored profile 0 after warm reset
Z1         Restore stored profile 1 after warm reset
&C0        Force RLSD active regardless of the carrier state
&C1        Allow RLSD to follow the carrier state
&D0        Interpret DTR ON-to-OFF transition per &Qn: 0,5,6 Ignores DTR. 1,2,3,4 Hangs up
&D1        Interpret DTR ON-to-OFF transition per &Qn: 0,1,4,5,6 Asynchronous escape. 2,3 Hangs up
&D2        Interpret DTR ON-to-OFF transition per &Qn: &Q0 through &Q6 The modem hangs up
&D3        Interpret DTR ON-to-OFF transition per &Qn: 0,1,4,5,6 Performs soft reset. 2,3 Hangs up
&F0        Restore factory configuration 0
&F1        Restore factory configuration 1
&G0        Disable guard tone
&G1        Disable guard tone
&G2        Enable 1800 Hz guard tone
&J0        Set S-Register response only for compatibility
&J1        Set S-Register response only for compatibility
&K0        Disable DTE/DCE flow control
&K3        Enable RTS/CTS DTE/DCE flow control
&K4        Enable XON/XOFF DTE/DCE flow control
&K5        Enable transparent XON/XOFF flow control
&K6        Enable both RTS/CTS and XON/XOFF flow control
&L0        Select dial up line operation
&M0        Select direct asynchronous mode
&P0        Set 10 pps pulse dial with 39%/61% make/break
&P1        Set 10 pps pulse dial with 33%/67% make/break
&P2        Set 20 pps pulse dial with 39%/61% make/break
&P3        Set 20 pps pulse dial with 33%/67% make/break
&Q0        Select direct asynchronous mode
&Q4        Select Hayes AutoSync mode
&Q5        Modem negotiates an error corrected link
&Q6        Select asynchronous operation in normal mode
&R0        CTS tracks RTS (async) or acts per V.25 (sync)
&R1        CTS is always active
&S0        DSR is always active
&S1        DSR acts per V.25
&T0        Terminate any test in progress
&T1        Initiate local analog loopback
&T4        Allow remote digital loopback
&T5        Disallow remote digital loopback request
&V         Display current configurations
&W0        Store the active profile in NVRAM profile 0
&W1        Store the active profile in NVRAM profile 1
&X0        Select internal timing for the transmit clock
&X1        Select external timing for the transmit clock
&X2        Select slave receive timing for the transmit clock
&Y0        Recall stored profile 0 upon power up
&Y1        Recall stored profile 1 upon power up
&Zn=x      Store dial string x (to 34) to location n (0 to 3)
%E0        Disable line quality monitor and auto retrain
%E1        Enable line quality monitor and auto retrain
%E2        Enable line quality monitor and fallback/fall forward
\Kn        Controls break handling during three states:

When modem receives a break from the DTE

\K0,2,4    Enter on-line command mode, no break sent to the remote modem
\K1        Clear buffers and send break to remote modem
\K3        Send break to remote modem immediately
\K5        Send break to remote modem in sequence with transmitted data

When modem receives \B in online command state:

\K0,1      Clear buffers and send break to remote modem
\K2,3      Send break to remote modem immediately
\K4,5      Send break to remote modem in sequence with transmitted data

When modem receives break from the remote modem:

\K0,1      Clear data buffers and send break to DTE
\K2,3      Send a break immediately to DTE
\K4,5      Send a break with received data to the DTE


\N0        Select normal speed buffered mode
\N1        Select direct mode
\N2        Select reliable link mode
\N3        Select auto reliable mode
\N4        Force LAPM mode
\N5        Force MNP mode
\V0        Connect messages are controlled by the command settings X, W, and S95
\V1        Connect messages are displayed in the single line format
+H0        Disable RPI
+H1        Enable RPI and set DTE speed to 19200 bps
+H2        Enable RPI and set DTE speed to 38400 bps
+H3        Enable RPI and set DTE speed to 57600 bps
+H11       Enable RPI+ mode
-SDR=0     Disable Distinctive Ring
-SDR=1     Enable Distinctive Ring Type 1
-SDR=2     Enable Distinctive Ring Type 2
-SDR=3     Enable Distinctive Ring Type 1 and 2
-SDR=4     Enable Distinctive Ring Type 3
-SDR=5     Enable Distinctive Ring Type 1 and 3
-SDR=6     Enable Distinctive Ring Type 2 and 3
-SDR=7     Enable Distinctive Ring Type 1, 2, and 3
-SSE=0     Disable DSVD
-SSE=1     Enable DSVD

* Serial interface operation only

ECC Commands

%C0        Disable data compression
%C1        Enable MNP 5 data compression
%C2        Enable V.42 bis data compression
%C3        Enable both V.42 bis and MNP 5 compression
\A0        Set maximum block size in MNP to 64
\A1        Set maximum block size in MNP to 128
\A2        Set maximum block size in MNP to 192
\A3        Set maximum block size in MNP to 256
\Bn        Send break of n x 100 ms

MNP 10 Commands

-K0        Disable MNP 10 extended services
-K1        Enable MNP 10 extended services
-K2        Enable MNP 10 extended services detection only
-SEC=0     Disable MNP10-EC
-SEC=1,[]  Enable MNP10-EC and set transmit level 0 to 30
           (0dBm to -30dBm)

W-Class Commands

*B         Display list of permanently blacklisted numbers
*D         Display list of delayed numbers

Caller ID Commands

#CID=0     Disable Caller ID
#CID=1     Enable Caller ID with formatted presentation
#CID=2     Enable Caller ID with unformatted presentation

Fax Class 1 Commands

+FCLASS=n  Service class
+FAE=n	   Data/fax auto answer

Fax Class 2 Commands

+FCLASS=n  Service class
+FAA=n	   Adaptive answer
+FCLASS=   Service class
+FCR=      Capability to receive
+FDCC=     DCE capabilities parameters
+FDIS=     Current sessions parameters
+FPTS=     Page transfer status
+FREV?     Identify revision

Voice/Audio Commands

#MDL?	   Identify model
#MFR?	   Identify manufacturer
#REV?      Identify revision level