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Appendix F - MMH2834 Modem Commands
F.2 Dialing Action Commands
Dial Command D
The letter D in a command causes the MMH2834 to dial the telephone number immediately
following it. For example, if you enter ATD5551212 and hit RETURN, the MMH2834 dials the
number 555-1212.
The MMH2834 gives you several choices of dialing methods. You can use tone or pulse dialing,
by inserting a letter T or a P in the command string. (See section F.3 on Dial Modifiers).
You can also configure the modem to either wait for and detect dial tones and busy signals
(which we call “Wait-for-Dial-Tone” dialing or “Smart” dialing), or work with timed pauses without
dial tone and busy signal detection (which we call “Blind” dialing; see section F.6, Result Codes.)
Note: There is another method of dialing, called “DTR Dialing”, where by manipulating the DTR
signal on pin 20 of the RS232C/V.24 interface, a number stored in the modem's memory is
automatically dialed. See section on DTR Dialing ($D command) for details.
Continuous Redial A: or :
If you select the Wait-For-Dial-Tone method of dialing (see X3 or X4 command), you can
command the MMH2834 to continuously redial (up to 10 redials for DOC units) a busy number
until your call is answered. This is done with the A: command.
This command would be used only if you had already reached a busy number after executing a
normal dial command. You simply enter A: (you need not enter AT, nor do you need to hit
RETURN), and the modem will redial the number for you. If you again reach a busy signal, it
redials again and again until it no longer detects a busy signaF. You can stop the MMH2834 from
redialing by pressing any key.
Another method used to cause the modem to redial a phone number continuously is to enter a
colon : at the end of the phone number. The result is the same as if you had entered A: after
personally observing that the number was busy on the first dialing attempt. Using the colon in the
dialing string is a step saver.
Dialing a Stored Number N
A telephone number that you have stored in the MMH2834’s number memory may be
automatically dialed by entering ATNn where n = 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9. For example, a
number stored at N3 would be dialed by entering ATN3 and RETURN. Do not include the letter D
in this command, or the stored number will be erased (also see section F.4, Phone Number
Memory Commands).
DTR Dialing $D
An alternate method of causing the MMH2834 to automatically dial is DTR Dialing. Data Terminal
Ready (DTR) is a signal that comes into the modem from the terminal or computer to whichit is
connected, on pin 20 of the RS232C interface. In DTR dialing, the modem automatically dials a
stored number as soon as it receives a high DTR signal. The DTR dialing method is popular in
synchronous applications.
To activate DTR Dialing, enter AT$D1 and hit RETURN. The modem dials the phone number
stored in the N0 location of memory when it receives a high DTR signal. DTR must remain high
for the duration of the call, until disconnect. To deactivate DTR dialing, enter AT$D0 and hit
RETURN.