Comtech EF Data CDM-625A - Manual (Page 148)

CDM-625A Advanced Satellite Modem MN-CDM625A
Front Panel Operation Revision 3
6–22
The modem automatically selects the actual scrambler used for Normal, depending on the exact
operating mode:
• If framing = IBS/D&I, the IESS-309 scrambler is used.
• If Reed-Solomon is on but IBS/D&I is off, its frame synchronous scrambler is used per
IESS-310, App. H. An exception to this is legacy EF Data Reed-Solomon, which uses a
proprietary modified V.35 scrambler instead.
• If framing = EDMAC/2/3 and Reed-Solomon is OFF, its frame synchronous scrambler is used.
• If configured for TPC (Turbo) encoding and all of the above settings are off, the TPC frame
scrambler is used except for 8-QAM. For CDM-570 compatibility, TPC with 8-QAM uses the
V.35 scrambler.
• ITU V.35 scrambler (Intelsat variant) is the default scrambler when all of the above settings
are OFF.
When you select IESS, the default ITU V.35 scrambler specified in IESS-315 takes priority over all
“normal” scramblers and is used instead. Therefore, for many operating modes, the two
scrambler selections are redundant.
When using TPC and Carrier-in-Carrier simultaneously, the IESS-315 (V.35) scrambler is the only
permitted choice.