2-Wire Dial-Up Operation; Dial Backup - Motorola V.3400 User Manual

Note
DTR must be held high in 2-wire or 4-wire leased line oper-
ation. This is accomplished by DTE control, wiring pin 20
of the digital interface cable high, or by selecting the
option, IGNORES DTR. If DTR is terminal controlled, loss
of synchronization can be corrected by cycling DTR. This
causes the modem to initiate the 2-wire training sequence.
DSR goes off during the training procedure.

2-wire Dial-up Operation:

Connection to the telephone network is through the LINE jack. A
standard telephone can be connected to the AUX jack for manual
dialing.

Dial Backup

Dial backup allows the modem to switch to a dial backup mode if the
data connection on the leased line is unacceptable for communications.
This can be accomplished in two ways:
• Automatic - backup due to extended loss of carrier or 4
unsuccessful retrains in 3 minutes
• Manual - user determined using front panel controls or AT
commands
Caution
In leased line operation, if both units have autodial backup
enabled, one must be configured for forced answer. This
prevents both units from dialing if the leased line fails.
Both methods will cause the modem to dial the prestored autodial
number. The originate modem will wait for 5 seconds and then initiate
the call. The answer modem will wait for a ring. The modems then train
and begin communicating over the dial-up line. If the dial connection is
unsuccessful after three attempts, a retrain on the leased line will be
initiated.
V.3400
AT Commands
5-35