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Dialing Pause
Enter a comma in the dialing string to make the modem pause while dialing. This pause
lasts two seconds (North American models) or four seconds (U.K. and International models)
for each comma entered. You can force longer pauses by entering multiple commas, or you
can change the length of the pause caused by a comma by setting register S8 to any value
from 0 through 255 seconds (North American models), 4 through 7 seconds (U.K. models)
or 4 through 255 seconds (International models).
Each comma in a dialing command counts as one of the 60 allowed characters.
:
Continuous Redial
Enter a colon (:) as the last character of a dialing command, to cause the modem to
continuously redial the number, if it detects a busy signal, until the call is answered. North
American models are limited to 10 redials. You must select smart dialing (X3 or X4) for this
to work. (Not available in U.K. or International models.)
Note:
This command has largely been superseded by software-based continuous redial features.
;
Return to Command Mode After Dialing
Enter a semicolon (;) as the last character of a dialing command to cause the modem to
return to command mode immediately after executing the command instead of waiting for a
carrier signal and going online.
For example, type ATDT5551212; to tone-dial the number and immediately go back into
command mode. The semicolon is useful when modem data transfer is not desired, as in
voice communications, or in applications using touch tones as a data entry method, such as
bank-by-phone.
!
Flash On-Hook
Some switchboard systems react to a momentary on-hook condition. Insert an exclamation
mark into the dialing command to cause the modem to "flash" on-hook for half a second,
just as if you had pressed the switch hook on a telephone set for half a second. (With U.K.
models, the exclamation mark causes the modem to flash on-hook for 90 milliseconds.)
For example, to flash on-hook to transfer to extension 5678 after dialing the number 555-
1234, type ATDT5551234,,!5678. The commas cause a 4-second pause.
@
Quiet Answer
Use the @ command to access a system that does not provide a dial tone. The @ command
causes the modem to wait before processing the next character in the dialing string. The
wait is for one or more rings back followed by five seconds of silence.
For example, ATDT5551212@6313550 causes the modem to dial the first number (555-
1212), then wait for the time specified in register S7 for at least one ringback and five
seconds of silence. If the modem detects a busy signal, it hangs up and generates a BUSY
result code. If it does not detect five seconds of silence, it hangs up and generates a NO
ANSWER result code. If it does detect five seconds of silence, it dials the second number
(631-3550).
Chapter 3 - AT Commands
28
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