Paradise Datacom P300 Series Installation & Operating Handbook page 136

The disadvantage of operating without a TS32 Multiframe is that the
synchronous IBS scrambler cannot be used, and the `Normal` scrambler option
selects INTELSAT V.35. This results in an increase in the error rate, as the
V.35 scrambler multiplies any errors on the channel by a factor of three.
Both options lead on to the following question:
Change, Tx/Rx, Service, Custom, IBS, Backward Alarm Menu
A Backward Alarm is sent (Tx) or detected (Rx) as normal
No Backward Alarm is sent (Tx) or received (Rx). This is a very useful facility to
have to lose, but for maximum ESC operation this selection does free up one
further bit of the overhead (TS32 bit 3) to carry ESC information.
If both the TS32 Multiframe and Backward Alarm options have been selected as
following screen is displayed. If either the Backward Alarm facility or the TS32 Multiframe has been
disabled, then this menu is skipped.
Change, Tx/Rx, Service, Custom, IBS, Back' Alm mode Menu
A single backward alarm operates as normal
The modem transmits or receives four independent backward alarms, using the
form `c` outputs and backward alarm inputs normally used for IDR operation.
This allows a single IBS Tx carrier feeding multiple Rx sites (each site receiving
part of the data in the Tx carrier), to individually indicate to each site a failure of
the return carriers from those sites. The sequence in which these four alarms
are carried in the IBS overhead may be changed under
Finally, all paths through these menus arrive at the following question:
Change, Tx/Rx, Service, Custom, IBS, Overhead Mode Menu
This final option is the most powerful of the features in Custom IBS.
The standard 16/15 (6.7%) IBS/SMS overhead is used. The ESC rate available
is a fixed proportion of the main data rate (but may be manipulated within limits
P300H P300 Series Modem Installation and Operating Handbook
Backward Alarm:[?]
1=Normal 2=No Backward Alarm facility
IBS Backward Alarm: [?]
1=Normal (single) 2=Four independent alarms
Overhead Mode: [?]
1=Normal 2=Min o/h to provide set ESC
, then the
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