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Chapter 5 - Command Mode
5.4 Dialing Commands
5.4.1 Dialing Action Commands
Dial Command D
The letter D in a command causes the modem to dial the telephone number immediately following it.
For example, if you enter ATD5551212 and hit RETURN, the modem dials the number 555-1212.
The D command is also used in conjunction with a telephone set for manual dialing. You dial the
number on your telephone set, and after hearing the answer tone on your handset, you type ATD on
your keyboard and hit RETURN. Then hang up the headset. Unless you have a specific need to dial
in this manner, we recommend you use the first method, where the telephone number is entered on
your keyboard.
The modem 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 5.4.2 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 on “X” Command.)
Note: There is another method of dialing, called “DTR Dialing”, where by manipulating the DTR
signal on pin 20 of the RS-232C/V.24 interface, a number stored in the modem's memory is
automatically dialed. See description of $D command (in this section) for details.
Continuous Redial (not used in BAI) A: or :
If you select the Wait-For-Dial-Tone method of dialing (see X3 or X4 command), you can command
the modem to continuously redial (up to 10 re-dials 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 re-dials again and
again until it no longer detects a busy signal. You can stop the modem from re-dialing 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 modem’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 5.4.3., on Phone Number Memory Commands).
DTR Dialing $D
An alternate method of causing the modem to automatically dial is DTR Dialing. Data Terminal Ready
(DTR) is a signal that comes into the modem from the terminal or computer to which it is connected,
on pin 20 of the RS-232C 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.