Chapter 4 - V.22bis Commands
Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide
21
V.22bis Call Control Commands
D
Dial
This command directs the modem to go on-line, dial according to the string entered and attempt to establish a
connection. If no dial string is supplied, the modem will go on-line and attempt the handshake in originate mode.
Note: If the ATD command is issued before the S1 register has cleared, the modem will respond with the NO
CARRIER result code.
The modem will behave as a data modem and will attempt to connect to another data modem. The modem will have
up to the period of time specified by register S6 or S7 to wait for carrier and complete the handshake. If this time
expires before the modem can complete the handshake, the modem will go on-hook with the NO CARRIER
response.
This command will be aborted while in progress (but before the completion of the handshake) upon receipt of any
DTE character.
Dial Modifiers
The valid dial string parameters are described below. Punctuation characters may be used for clarity, with
parentheses, hyphen, and spaces being ignored.
Syntax
D<string>
Defined Values
<string> Character string corresponding to the selected option(s).
0-9 DTMF digits 0 to 9.
*
The 'star' digit (tone dialing only).
#
The 'gate' digit (tone dialing only).
A-D DTMF digits A, B, C, and D. Some countries may prohibit sending of these digits during dialing.
L
The modem will re-dial the last valid telephone number. The L must be immediately after the D with all the
following characters ignored.
P Pulse dial the numbers that follow until a "T" is encountered. Affects current and subsequent dialing. Some
countries prevent changing dialing modes after the first digit is dialed.
T
Tone dial the numbers that follow until a "P" is encountered. Affects current and subsequent dialing. Some
countries prevent changing dialing modes after the first digit is dialed.
R This command will be accepted, but not acted on.
!
Flash. the modem will go on-hook for a time defined by the value of S29. Country requirements may limit the
time imposed.
W The modem will wait for dial tone before dialing the digits following "W". If dial tone is not detected within the time
specified by S7 (U.S.) or S6 (other countries), the modem will abort the rest of the sequence, return on-hook, and
generate an error message.
@ The modem will wait for at least 5 seconds of silence in the call progress frequency band before continuing with
the next dial string parameter. If the modem does not detect these 5 seconds of silence before the expiration of
the call abort timer (S7), the modem will terminate the call attempt with a NO ANSWER message. If busy
detection is enabled, the modem may terminate the call with the BUSY result code. If answer tone arrives during
execution of this parameter, the modem handshakes.
& Wait for credit card dialing tone before continuing with the dial string. If the tone is not detected within the time
specified by S7 (U.S. models) or S6 (other countries), the modem will abort the rest of the sequence, return on-
hook, and generate an error message.
,
The modem will pause for a time specified by S8 before dialing the digits following ",".
;
Return to command state. Added to the end of a dial string, this causes the modem to return to the command
state after it processes the portion of the dial string preceding the ";". This allows the user to issue additional AT
commands while remaining off-hook. The additional AT commands may be placed in the original command line
following the ";" and/or may be entered on subsequent command lines. The modem will enter call progress only
after an additional dial command is issued without the ";" terminator. Use "H" to abort the dial in progress, and go
back on-hook.
^
Toggles calling tone enable/disable; applicable to current dial attempt only.
( ) Ignored; may be used to format the dial string.
-
Ignored; may be used to format the dial string.
<space> Ignored; may be used to format the dial string.
<i> Invalid character; will be ignored.
>
If enabled by country specific parameter, the modem will generate a grounding pulse on the EARTH relay output.
