Modem AT Commands
- A/
- Re-execute command
- ATA
- Answer command
- ATBn
- Set CCITT or Bell Mode
Command options:- B0
- Selects CCITT V.22bis, V.22, and V.21 standards for communication at 2400, 1200, and 300 bps
- B1
- Selects Bell 212A and 103 standards for communication at 1200 and 300 bps (default)
- ATCn
- Carrier control
Command options:- C0
- Not permitted; returns ERROR result code
- C1
- Normal transmit carrier switching (default)
- ATDn
- Dial
ATD parameters (may be combind):- L
- Dials the last string that was dialed
- P
- Use Pulse dialing
- T
- Use DTMF (tone) dialing
- R
- Reverse mode. Allows the modem to call an originate-only modem by forcing the call into “answer mode”. Must be entered at the last character of the command string
- !
- Hookflash. Causes the modem to go on-hook for 700 milliseconds and then off-hook
- @
- Listen for 5 seconds of silence before continuing the dialing
- W
- Wait for a dial tone before dialing
- &
- Wait for “AT&T Bong” before continuing
- ,
- Pause for number of seconds specified in S8 register
- ;
- Return to command mode after dialing
- ^
- Turn on 1300Hz calling tone
- S=n
- Dial number stored in memory previously using the AT&Zn command
- (phone number)
- Dial (phone number) entered
- ATEn
- Command echo
Command Options:- E0
- Inhibits the echoing of commands
- E1
- Enables the echoing of commands (default)
- ATHn
- Hang up
Command Options:- H0
- Causes the modem to go on-hook or hang up
- H1
- Causes the modem to go off-hook or pick up the line
- ATIn
- Identification and checksums
Command Options:- I0
- Reports the product code
- I1
- Reports the hardware ROM checksum
- I2
- Performs a checksum on the firmware ROM
- I3
- Reports firmware revision level
- I4
- Reports OEM specified product capabilities
- I5
- Reports the country code number
- ATLn
- Control Speaker Volume
Command Options:- L0
- Selects low speaker volume
- L1
- Selects low speaker volume
- L2
- Selects medium speaker volume
- L3
- Selects high speaker volume
- ATMn
- Control Speaker On/Off
Command Options:- M0
- Speaker is always off
- M1
- Speaker goes off while receiver a carrier (default)
- M2
- Speaker is always on
- M3
- Speaker off while dialing or receiving carrier, but on during answering
- ATNn
- Automode Enable
Command Options:- N0
- Automode detection is disabled. A subsequent handshake will be conducted according to the contents of S37 or, if S37 is zero, according to the most recently sensed DTE speed.
- N1
- Automode detection is enabled. A subsequent handshake will occur at the best speed supported by both modems. The value of the ATB command is ignored. (default)
- ATOn
- Return to the on-line state
Command Options:- O0
- Causes the modem to return to the data mode
- O1
- Causes the modem to retrain and the return to the data mode
- ATP
- Set pulse dial as default
- ATQn
- Result code display
Command Options:- Q0
- Allows the modem to send result codes to the DTE (default)
- Q1
- Prohibits the modem from sending result codes to the DTE
- ATSn
- Read or write to S registers
Command Options:- Sn?
- Reports the value of S-register n
- Sn=x
- Sets S-register n to the value of x
- ATT
- Sets tone dial as default
- ATVn
- Select word or digit result codes
Command Options:- V0
- Displays result codes in numeric format
- V1
- Displays result codes in verbose format (default)
- ATWn
- Negotiation message control
Command Options:- W0
- Error-correction call progress not reported (default)
- W1
- Error-correction call progress reported
- W2
- Error-correction call progress not reported, and CONNECT XXXX message reports DCE (line) speed
- ATXn
- Select result code reporting
Command Options:- X0
- Modem ignores dial tone and busy signal. Sends CONNECT message when a connection is established by blind dialing
- X1
- Modem ignores dial tone and busy signal. Sends CONNECT XXXX message reflecting data rate when a connection is established by blind dialing
- X2
- Modem ignores busy signal but waits for dial tone before dialing. Sends CONNECT XXXX message reflecting data rate when a connection is established
- X3
- Modem ignores dial tone. Sends CONNECT XXXX message reflecting data rate when a connection is established by blind dialing
- X4
- If dial tone is not detected, sends NO DIAL TONE message. If busy signal is detected, sends BUSY message. Sends CONNECT XXXX message refelecting data rate when a connection is established. (default)
- ATYn
- Control long space disconnect
Command Options:- Y0
- Disable long space disconnect (default)
- Y1
- Enable long space disconnect. The modem will send a long space of four seconds prior to going on-hook
- ATZn
- Reset and restore configuration profile
Command Options:- Z0
- Resets the modem and loads stored profile 0
- Z1
- Resets the modem and loads stored profile 1
- AT&Cn
- Data Carrier Detect (DCD) Options
Command Options:- &C0
- Maintains as ON status for the Data Carrier Detect (default)
- &C1
- Uses the actual state of the carrier from the remote modem for the Data Carrier Detect (recommended)
- AT&Dn
- Data Terminal (DTR) Options
Command Options:- &D0
- Non-standard (differs on each modem)
- &D1
- Non-standard (differs on each modem)
- &D2
- DTR going off triggers modem disconnect, sends OK result code, and disables auto answer while DTR is OFF. (default)
- &D3
- Non-standard (differs on each modem)
- AT&F
- Restore factory configuration
- AT&Gn
- Set guard tone
Command Options:- &G0
- Disable guard tone generation (default)
- &G1
- Disable guard tone generation
- &G2
- Enable 1800Hz guard tone generation
- AT&Jn
Telephone Jack Selection
Command Options:
- &J0
- Set jack type to RJ-11, RJ41S, or RJ-45S type phone jack (default)
- &J1
- Set jack type to RJ-12 or RJ-13 type phone jack
- AT&Kn
- DTE/Modem Flow Control
Command Options:- &K0
- Disables flow control
- &K3
- Enables RTS/CTS flow control (default)
- &K4
- Enables XON/XOFF flow control
- &K5
- Enables transparent XON/XOFF flow control
- AT&Ln
- Line type selection
Command Options:- &L0
- Selects dial-up line (default)
- &L1
- Selects leased line
- AT&Mn
- Communication Mode
Command options vary with modem type. - AT&Pn
- Select pulse dialing make/break ratio
Command Options:- &P0
- Sets a 39/61 make/break ratio at 10 pps (default)
- &P1
- Sets a 33/67 make/break ratio at 10 pps
- AT&Qn
- Asyhchronous/Sychronous mode select
Command Options:- &Q0
- Selects asynchronous operation in the Direct mode. In this mode, the DTE speed must match the telco line speed
- &Q1
- Selects synchronous connect mode with async off-line command mode
- &Q2
- Selects synchronous connect mode with async off-line command mode. The modem automatically dials the number stored in slot 0 when it detects an OFF-to-ON transition on DTR.
- &Q3
- Selects synchronous connect mode. This mode allows DTR to act as a talk/data switch. The call is manually dialed while DTR is OFF. When DTR becomes active, the handshake proceeds.
- &Q4
- Reserved. Differs on different modems.
- &Q5
- Reserved. Differs on different modems.
- &Q6
- Selects asynchronous operation in Normal mode (Speed Buffering). In this modem, the DTE speed can differ from the telco line speed.
- AT&Rn
- RTS/CTS option
Command Options:- &R0
- In synchronous mode, CTS tracks the state of RTS. The RTS-to-CTS delay is defined by S-register 26 (default)
- &R1
- In synchronous mode, CTS is always on, and RTS is ignored
- AT&Sn
- DSR option
Command Options:- &S0
- DSR will remain on at all times (default)
- &S1
- DSR will become active after answer tone has been detected and inactive after the carrier has been lost. (recommended)
- AT&Tn
- Testing and Diagnostic
Command Options:- &T0
- Terminates any test currently in progress
- &T1
- Initiates a local analog loopback in accordance with CCITT V.54 L3 during which verifies the path between the local DTE and the local modem
- &T4
- Allows the modem to respond to a request from a remote modem for a remote digital loopback test (default)
- &T5
- Prohibits the modem from granting a request from a remote modem for a remote digital loopback test
- &T6
- Initiates a remote digital loopback in accordance with CCITT V.54 L2 during which characters are transmitted to the remote modem and then looped back to the local modem
- &T7
- Initiates a remote digital loopback with self-test
- &T8
- Initiates a local analog loopback with self-test
- AT&V
- View current configuration profiles
- AT&Wn
- Store user profile
Command Options:- &W0
- Save as user profile 0
- &W1
- Save as user profile 1
- AT&Xn
- Select sychronous clock source
Command Options:- &X0
- Internal timing. (default)
- &X1
- External timing. The local DTE sources determine the clock signal
- &X2
- Slave receive timing. The modem derives the clock signal from the incoming carrier.
- AT&Yn
- Designate default user profile
Command Options:- &Y0
- Selects user profile 0
- &Y1
- Selects user profile 1
- AT&Zn
- Store telephone numbers
Command Options:- &Zn=x
- Store phone number x into dialing slot n (n=0-3)
- AT\Gn
- Modem-to-Modem flow control
Command Options:- \G0
- Disables XON/XOFF flow control (default)
- \G1
- Enables XON/XOFF flow control
- AT\Kn
- Break Control
Command options vary between different modems - AT\Nn
- Operation Mode Control
Command Options:- \N0
- Select normal speed buffering mode
- \N1
- Select direct mode
- AT%Cn
- Compression control
Command Options:- %C0
- Disable data compression
- %C1
- Enable data compression (default)
- AT%En
- Enable/Disable auto-retrain
Command Options:- %E0
- Disables auto-retrain (default)
- %E1
- Enables auto-retrain
- AT%L
- Report received signal level
- At%Q
- Report line signal quality