0049-1800-xxx 326X V.34, V.34-SDC and V.32bis Series Modem – USER’S GUIDE 02/23/2010
Rev. A
Page 49
of
205
Option Set 4 – Sync Leased Line Applications With Dial Restoral (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 326X Series Modem at both ends of the leased line to
implement restoral operation.
Option Set 4 configures the modem for a general restoral application (see Table 4-1). The modem uses
the adaptive rate feature in the V.34 or V.32bis Auto modes. This 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 its maximum rate over the dial line, and falls back to lower speeds if required. After an hour, the
modem returns to the leased line.
If you operate your modems in leased-line mode with Option Set 4, and
one
modem has software
Revision 7.8 or 7.9, set the
Fast Call
parameter (AT
*
FC, Modulation Opts Menu) to Off in
both
modems.
Option Set Descriptions – 326XFAST-SDC Modems
Option Set 1—Async Calls to Central Site
Option Set 1 in the 326X-SDC product functions the same as Option Set 1 above.
Option Set 2—Sync Dial A/B Restoral
Option Set 2 satisfies the needs of a synchronous point-to-point digital link restoral application (see Table
4-2).
With this option set, the
Clock
is set to External as network timing is provided by the DSU/CSU.
NOTE
: With this option set, (for Raymar-Telenetics and Motorola DSU/CSUs as well as non-Telenetics
and non-Motorola DSU/CSUs), the DSU’s restoral configuration should be set to
Timing
=Internal.
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.
