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53
CHAPTER 5: Command Mode
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 Series II 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 Series II 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 $D
An alternate method of causing the Series II Modem to automatically
dial is DTR Dialing. Data Terminal Ready (DTR) is a signal that comes
into the modem from the terminal or computer to which it is
connected, on pin 20 of the RS232C interface. In DTR dialing, the
modem automatically dials a stored number as soon as it receives a high
DTR Signal. The DTR dialing method is popular in synchronous appli-
cations.
To activate DTR Dialing, enter AT$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.
Note that when you use DTR Dialing in a synchronous application, you
need to make sure DIP-Switch #8 is in the UP position to disable V.25bis
Command mode.