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Chapter 5 – AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 41
Call Control Commands
Command: D Dial
Description: 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.
If +FCLASS=0 is selected, 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 in progress upon
receipt of any DTE character before completion of the handshake.
If +FCLASS=1, 1.0, or 2 is selected, the modem will behave as a facsimile
modem and attempt to connect to a facsimile machine (or modem) by
entering the HDLC V.21 channel 2 receive state (as if +FRH=3 had been
issued). This command will be aborted upon receipt of any DTE character
if the modem has not finished dialing. In this case, the modem will go on-
hook and return to command mode after displaying the NO CARRIER
message. If the modem has finished dialing, it proceeds as if the +FRH=3
command has been issued. (Refer to the +FRH command to determine
how the modem behaves following this stage.)
Dial Modifiers
The valid dial string parameters are described below. Punctuation
characters may be used for clarity, with parentheses, hyphen, and spaces
being ignored.
Defined Values: Character string <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 Re-dial last number: 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 Select pulse dialing: Pulse Dialing is used in the dialed numbers that
follow until a T command is encountered. Affects current and
subsequent dialing. Some countries prevent changing dialing modes
after the first digit is dialed.
T Select tone dialing: Tone Dialing is used in the dialed 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.
S=n Dial the number stored in the directory (n = 0 to 3). (See &Z.)
! Flash: the modem will go on-hook for a time defined by the value of
S29. Country requirements may limit the time imposed.
W Wait for dial tone: 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 (US) or S6 (W-class), the modem will abort the rest
of the sequence, return on-hook, and generate an error message.
@ Wait for silence: 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