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(Please note that this is the basic AT Command set.  Many modems do NOT conform to this command set.  However, most of these commands remain the same, or similar from modem to modem.)

Quickly Referenced Commands

AT  -  "Attention!"

+++  -  "Escape Sequence"

,  -  "Pause"

A/  -  "Repeat Sequence"

ATA  -  "Answer Mode"

Bn  -  "Select Communication Protocol"

Cn  -  "Transmission Carrier"

Dn  -  "Dial Control"

En  -  "Echo"

Fn  -  "Data Mode Echo"

Hn  -  "Hook Select"

In  -  "Report Modem Information"

Ln  -  "Set Speaker Volume"

Mn  -  "Set Speaker Mode"

Nn  -  "Automode Selection/Detection"

On  -  "Retrain Selection"

P  -  "Pulse Dialing"

Qn  -  "Result Codes to DTE"

Sn=x  -  "Status Registers"

T  -  "Tone Dialing"

Vn  -  "Format of Result Code"

Wn  -  "Extended Result Codes"

Xn  -  "Result Codes for Call Progress"

Yn  -  "Long Space Disconnect"

Zn  -  "Soft Reset and Restore"

Verbosely Referenced Commands

AT -  "Attention!"  -  This command tells the modem that a command follows it.

+++  -  "Escape Sequence"  -  This command initiates an escape sequence to return the modem to the on-line command mode.

,  -  "Pause"  -  The Comma normally initiates a 1-5 second pause, however is sometimes used as a command separator in +MS and other commands.

A/  -  "Repeat Sequence"  -  This repeats the previous command.  This command will not function properly if preceded by the AT command or followed by <CR>.

ATA  -  "Answer Mode"  -  This command initiates the modem into an auto-answer mode.

Bn  -  "Select Communication Protocol"  -  This command selects the v.22 or Bell 212A protocols for data calls.

    B0  -  ITU-T v.22 (300bps or 1200bps)

    B1  -  Bell 212A (300bps or 1200bps)

    (There is sometimes a B2 that enables v.23)

Cn  -  "Transmission Carrier"  -  This command controls the switching of the transmit carrier.

    C0  -  Transmit carrier disabled

    C1  -  Transmit carrier enabled

Dn  -  "Dial Control"  -  This command dials the phone number with accordance to the modifiers of n.

    DL  -  Redial the last dialed number

    DP  -  Pulse dial

    DR  -  Enable answer mode

    DS=x  -  Dial the stored telephone number in x

    DT  -  Tone dial

    DW  -  Resume dialing after dial tone is detected

    D,  -  Pause before dial

    D"555-4NET"  -  Letters enclosed in quotes will be dialed as their corresponding numbers on the dialpad.

    D!  -  Enable "flash".  (modem can go off hook for a specified amount of time before returning on hook)

    D@  -  Modem will wait for a quiet answer before dialing the rest of the dial string

En  -  "Echo"  -  This command controls whether the modem echos commands received by the DTE or not.

    E0  -  Echo Disabled

    E1  -  Echo Enabled

Fn  -  "Data Mode Echo"  -  This command controls whether the modem echos commands sent while in data mode.

    F0  -  Echo in data mode enabled

    F1  -  Echo in data mode disabled

Hn  -  "Hook Select"  -  This command determines whether the modem is on-hook (hangs up) or off-hook (picks up).

    H0  -  On-hook

    H1  -  Off-hook

In  -  "Report Modem Information"  -  This command reports selected information about the modem.

    I0  -  Modem model and speed

    I1  -  ROM checksum

    I2  -  Tests ROM checksum THEN reports it

    I6  -  Data connection info

    I7  -  Manufacturer and model info

Ln  -  "Set Speaker Volume"  -  This command controls the speaker volume of the modem.

    L0  -  Mute

    L1  -  Low volume

    L2  -  Medium volume

    L3  -  High volume

Mn  -  "Set Speaker Mode"

    M0  -  Disable speaker

    M1  -  Enable speaker until a carrier signal is detected

    M2  -  Enable speaker

    M3  -  Enable speaker after dialing but disable after a carrier signal is detected

Nn  -  "Automode selection/detection"  -  This command is usually more basic (a simple N0 for disabled, N1 for enabled) on 56k modems where automode is more often controlled by an s-register or the +MS command.  The full basic Nn command is included for completeness.

    N0  -  Disable automode

    N1, N2, N3, N4, and N5  -  Enable automode.  Originate mode and Answer mode v.XX attempts will vary from register to register.  The N2-N5 commands will not normally be used by 56k modems.

On  -  "Retrain Selection"  -  Confusing command that probably should never have been created as it uses an O rather than a 0 and can often be confused.  It enables or disables retraining.

    O0  -  Retraining disabled in on-line command mode

    O1  -  Retraining enabled in on-line command mode

P  -  "Pulse Dialing"  -  This command sets the modem to pulse dial.  This command can be duplicated by DP.

Qn  -  "Result Codes to DTE"  -  This command selects whether the modem sends result codes to the DTE or not.

    Q0  -  Enable result codes to DTE

    Q1  -  Disable result codes to DTE

Sn=x  -  "Status Registers"  -  This command writes to or reads data from S-register n.  The data written is represented in the place of x.  The data used in read mode is selected by the value in x.  S-registers can vary a great deal, please consult the AT Command Set specific to your modem when attempting to use these.

T  -  "Tone Dialing"  -  This command sets the modem to tone dial.  This command can be duplicated by DT.

Vn  -  "Format of Result Code"  -  This command selects the format for information-text and result codes.

    V0  -  Numeric format

    V1  -  Word (verbose) format

Wn  -  "Extended Result Codes"  -  This command enables selection of extended result codes.

    W0  -  Enables the CONNECT result codes to report the DTE speed.

    W1  -  Enables the CONNECT result codes to report the DTE speed.

    W2  -  Enables the CONNECT result codes to report the DCE speed.

Xn  -  "Result Codes for Call Progress"  -  This command selects tone detection and result code formatting options.

    X0  -  Disable busy and dialtone detection.  Result codes 0-4 enabled.

    X1  -  Disable busy and dialtone detection.  Result codes 0-5,10 enabled.

    X2  -  Disable busy detection, enable dialtone detection.  Result codes 0-6,10 enabled.

    X3  -  Enable busy detection, disable dialtone detection.  Result codes 0-5,7,10 enabled.

    X4  -  Busy and dialtone detection enabled.  Result codes 0-7,10 enabled.

Yn  -  "Long Space Disconnect"  -  This command tells the modem whether or not to disconnect if a 1.6 second break is detected.

    Y0  - Long space disconnect disabled

    Y1  -  Long space disconnect enabled

Zn  -  "Soft Reset and Restore"  -  Restores modem profiles that are saved in non-volatile RAM.  Refers itself to the &W command.

    Z  -  Soft Reset, basic default restore

    Z0  -  Restore setting 0

    Z1  -  Restore setting 1