D - Dial Command

Command Line Format
AT [cmds] D [Digits and Modifiers] [ ; [cmds] ] <CR>

Default
N/A

Stored by &Wn
N/A

Displayed by &V
N/A

Description
Instructs the modem to execute the Dialing Process (i.e., go off hook and process the dial string), which may lead to executing the Handshaking Process. The dial string is a combination of dial digits and dial modifiers. If the modem is off hook, it does not wait or attempt to detect dial tone before proceeding. The D command is not valid in the Online Command State or if either &Q2 or &Q3 is in effect.

The D command may only be followed by dial digits and modifiers (if any), except for when the ; is used: in this case, the ; (semicolon) may only be followed by commands (if any). Invalid dial modifiers in the dial string (e.g., "-") are ignored.

Refer to Dialing Process and the Handshaking Process.

Dial Digits
The dial digits include 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, #, and *.

Dial Modifiers
The following paragraphs describe the dial modifiers.
Only the S=n dial modifier has any suffixes. These are displayed by the &V command only when they are a part of a stored number (refer to the &Zn= command) except for P (Pulse) and T (Tone), which are also commands. Only P and T may be stored by the &Wn command.

P - Select Pulse Dialing - Instructs the modem to use pulse dialing. Dialed digits are pulse-dialed in subsequent digits of the current dial string and in all future dial strings until a T command or dial modifier is executed.

R - Originate Call In Answer Mode - Instructs the modem to go into the answer mode rather than the originate mode after executing the dial string and starting the handshake. The same result occurs if several R dial modifiers are in the same dial string.

S=n - Dial Stored Telephone Number - Indicates to the D command that the telephone dial string n, one of four such strings that may have previously been stored by an &Zn= command, is processed now.

T - Tone - Instructs the modem to send DTMF tones while dialing. Dialed digits are tone dialed until a P command or P dial modifier is selected.

W - Wait For Dial Tone - Executes the dial characters or modifiers following the command if a valid dial tone is detected. If no dialtone is detected before the specified time then the modem returns the NO DIALTONE result code and clears the call. If a busy signal is detected instead of dial tone, then the modem returns the BUSY result code and clears the call. Subsequent instructions in the dial string or on the command line are abandoned.

Comma (,) Pause - Instructs the modem to pause for the amount of time specified by S8 (in seconds) before processing the next character in the dial string. This modifier is also used as a command.

Quotes (") - Telephone numbers may be enclosed in double quote symbols ("). Enclosed characters may be digits or letters. Dial digits are interpreted as numbers. Letters are interpreted as digits according to the following chart. Quote symbols are used in pairs; the first of the pair begins the quoted string, the second of a pair ends the quoted string, for example, "HI-MODEM" would be converted to 4466336. Subsequent quotes may be used; that is, several sections of a dial string may be individually enclosed in quotes. If a closing quote is not sent to the modem before the dial command is ended (by <CR>or ;), then the modem treats the dial string as if a closing quote occurred before the ending character.

Letters           Digit                Letters           Digit             


ABC               2                    MNO               6                 


DEF               3                    PRS               7                 


GHI               4                    TUV               8                 


JKL               5                    WXY               9

Exclamation mark (!) - Flash - Instructs the modem to go on-hook (for a time that is specific to the country) then return off-hook. The modem, if capable, lowers the off-hook resistance 100 +/- 10 ms before going on-hook for the flash and returns the off-hook resistance to normal 100 +/- 10 ms after the flash. This causes the flash duration to be 200 ms plus the length of the flash. Flash is also called hookflash, or register recall.

@ - Wait For Quiet Answer - Instructs the modem to look for line signal (ringback) followed by 6.5 +/- 0.5 seconds of silence (no detectable signal in call progress frequency band) up to the time specified in S7.

If quiet answer is detected, the dial modifiers following the command are executed.

If busy is detected, the modem returns a BUSY result code and goes to the hang-up process, aborting further execution of the dial string.

Note: At least 6 seconds of silence are required to cover the ringing cadence of certain European countries.

Note: Busy signal detection is enabled during execution of the W, @, and $ dial modifiers.

$ - Wait for bong tone - Instructs the modem to wait for detection of the prompt tone as follows.

Note: This dial modifier is available in 28.8 kbits/s modems.

a. If the modem does not detect the tone before the S7 timeout occurs, then the call is terminated, and the NO DIALTONE result code is returned.

b. If the modem detects the prompt tone before the time limit, then the modem pauses 1 second and executes the remainder of the dial string.

The prompt tone detector responds to tone 2 at any level between 0 dBm and -30 dBm if it lasts at least 200 ms. The tone detector does not respond to the following:

1. Tones outside the call progress band of 375 to 550 Hz,

2. Tones whose duration is less than 200 ms,

3. Tones (such as busy tone) that go off and back on in less than 1 second.

Note: The Bellcore definition of the prompt tone is as follows:
Tone 1 for 60 ms, followed immediately by Tone 2. Tone 1: 941 and 1477 Hz, constant level, two tones. Tone 2: 440 and 350 Hz, decaying with time constant of 200 ms, ending after 940 ms. The level of tone 1 is -10 dBm/freq. The initial level of tone 2 is -10 dBm/freq. at-3TLP.
The suggested method of detecting bong tone is to measure the initial tone level, using a 50 ms observation interval. Check the level again after 230 ms, again with a 50-ms observation interval. Detect bong tone if the second level is 7 to 13 dB less than the first level, otherwise reject.

Security Dial
The following information describes the security stings.

Modifiers
Percent (%) dial modifier instructs the modem to end the number string and record the following security information. Security information is in the following format:

Syntax
%<mode>,[<key>],["<num>[,<gp>]"],"<password>",[<callback>]
or
Syntax
%<mode>,[<key>],["<num>[,<gp>]"],"<password>",["<callback>"]

Example
ATDT9,5551234%1,432efd,"12,3","secret12",HOME">CR>
or
Example
ATDT9,5551234%1,432efd,"12,3","secret12",122<CR>

<mode> =0,1,2,3, or 4. See %SPRT Security Mode - Outgoing Calls .

<key> The key to be used for the call. See %SKEY - Store Authentication Key Outgoing Call. This is a volatile value. If not present, the key stored with the -SKEY command is not used.

<userid> The user ID for the call. See %SUID - User ID Outgoing Calls.

<password> The password for the call. See %SPWD - Password Outgoing Calls.

<callback> The call back reference. See %SCBR - Call Back Reference Outgoing Calls.

Semicolon (;) - Return To Idle State - This dial modifier instructs the modem to return to the idle state and wait for more commands even though it has executed a dial command. The modem does not proceed to the Handshaking Process until an A or O or another D command is processed.

The semicolon dial modifier may be part of a stored telephone number and is executed by the dialing process regardless of how the dialing process is entered.
Syntax AT [cmds] D [dial-string] S[0|=n] [ignore]<CR>

where:

a. Other commands may precede the D command.

b. Non-stored dial string characters after the D may precede the S.

c. The S may be followed by 0 or =n, where n is 0-3. Invalid n causes an ERROR result code. If the character immediately following the S is not an = or a 0 then all characters after the S are ignored, and stored number 0 is dialed.

Result Codes
BUSY - if busy is detected (independent of Xn command selected).

NO DIALTONE - if X2 or X4 are selected and 1 second of dial tone is not detected. NO DIALTONE is also sent in response to a W dial modifier if dial tone is not detected within the time specified by S7.

ERROR - if the S=n dial modifier is processed and the n value is out of range (see the S dial modifier) or if the total number of characters in the command line plus the stored dial string exceeds the command buffer limit.

NO ANSWER - if quiet answer is not detected within time specified by S7.

Note: NO ANSWER result code is used only by the @ dial modifier.

OK - if aborted by DTR ON-to-OFF whenever certain combinations of &D and &Q are in effect. See the &D command; if the semicolon (;) dial modifier is processed in the dial string, or if aborted by a character from the DTE during the dialing process.

CONNECT - if a connection is made with another modem.

NO CARRIER - if no carrier signal is detected while the modem is attempting a connection.

Cross Reference
DTE signals - Carrier Detection , LEDs - CD

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