Motorola 326X V.34 - Manual (Page 71)

Configuring the Modem 4-9
Confi
guring
the Modem
With this option set, the local and remote modems are configured for SDC operation.
The modems default to Fast Call=Lvl3, and use LAPM error correction with
modified V.42bis data compression. Enable Option Set 2 in both the local and remote
modems, and ensure that Mode (AT
* SM) is set the same in both modems.
The modem uses the adaptive rate feature in the V.34 Auto modulation mode. This
ensures maximum throughput when line quality is poor.
Option Set 3—Sync Dial Only
Option Set 3 satisfies the needs of a synchronous dial application (see Table 4-2).
With Option Set 3, the modem provides the network timing (Clock=Internal).
Select a data rate at which the modem communicates with the DTE, using DTE Rate
(AT
* DE). Consult the description in Appendix A.
With this option set, the local and remote modems are configured for SDC operation.
The modems default to Fast Call=Lvl3, and use LAPM error correction with a
modified V.42bis data compression. Enable Option Set 3 in both the local and remote
modems, and ensure that Mode (AT
* SM) is set the same in both modems.
With Option Set 3, DTR=108.1 so that an off-to-on DTR transition instructs the
modem to connect to the telephone line. If the modem detects an incoming call, the
call is connected. If the modem does not detect an incoming call and Default Dial
(AT
* DA) is enabled, the modem dials the number specified. If Default Dial is
disabled, the modem refers to the Modulation Mode option (AT * MM). If set to
Answer, the modem goes off-hook and sends an answer-back tone. An on-to-off
DTR transition disconnects the modem from the telephone line. If DTR is low, the
modem does not auto-answer. DTR transitions govern how the modem answers and
disconnects calls. All options in the ACU OPT’S category are set for a typical
synchronous DTE.
The modem uses the adaptive rate feature in the V.34 Auto modulation mode. This
ensures maximum throughput when line quality is poor.
Option Set 4—Sync Leased Line with Dial Restoral; No ACU (Models 3261/
63/66/68)
Option Set 4 uses the modem’s leased line restoral feature. With this option set, the
modem operates primarily on a leased line unless that line fails. If so, the modem
automatically restores the connection over a single dial line. You must install a
326XFAST-SDC Modem at both ends of the leased line to implement restoral.
Option Set 4 configures the modem for a general restoral application (see Table 4-2).
The modem uses the adaptive rate feature in the V.34 Auto modulation mode. This
setting ensures maximum throughput when line quality deteriorates. If restoral
criteria are met, the modem automatically reroutes data traffic through the public
switched telephone network (PSTN) over a single dial line. At that time, the modem
attempts to run at 28.8 kbps over the dial line, and falls back to lower speeds if
required. After an hour, the modem returns to the leased line.
With Option Set 4, the modem provides the network timing (Clock=Internal).
Select a data rate at which the modem communicates with the DTE, using DTE Rate
(AT
* DE). Refer to the description in Appendix A.