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DMD50 Universal Satellite Modem
1920000 bps will result in an error message. In turn, the selection of the terrestrial framing
formats influences the satellite channel to terrestrial timeslot mappings in the following manner:
The selection of T1-D4, T1-ESF, or SLC-96 type terrestrial framing format limits the
terrestrial timeslots to values from 1 - 24.
The selection of PCM-30 or PCM-30C type terrestrial framing limits the terrestrial timeslots
to values from 1 - 15, 17 - 31. In these modes, terrestrial timeslot 16 is reserved for ABCD
signaling and may not be dropped or inserted.
The selection of PCM-31 or PCM-31C type terrestrial framing limits the terrestrial timeslots
to values from 1 - 31. Therefore, the terrestrial framing format should be identified via the
Drop Mode and Insert Mode entries prior to editing the Drop or Insert satellite channel to
terrestrial timeslot maps.
H.2.3.1
Insert Terrestrial Frame Source
The Insert Terrestrial Frame Source selection tells the Modem from where the Insert Terrestrial
Frame is coming.
External:
Internal:
The selection of the Insert Terrestrial Frame Source also influences the Buffer Clock selection in
the following manner:
When the Insert Terrestrial Frame Source selection is set to External, the received satellite data
will be clocked out of the Doppler Buffer based upon the clock recovered from the insert data
input. Therefore, the Buffer Clock selection will automatically be set to External and cannot be
modified. Attempts to select a different buffer clock will result in the error message INVALID
BUFFER CLOCK and the selection will not be allowed.
When the Insert Terrestrial Frame Source selection is set to Internal, the operator needs to specify
how data should be clocked out of the Doppler Buffer. In this case, the operator will be able to
select SCTE, SCT, RX SAT, or EXT EXC as the source for the Buffer Clock. Therefore, the
Insert Terrestrial Frame Source selection should be made prior to attempting to change the Buffer
Clock. In most instances, the Insert Terrestrial Frame Source selection will be set to External and
the Buffer Clock will automatically be set to External.
MN-DMD50 Revision 4
Indicates that the terrestrial frame is to be input via the Insert Data In
Port.
Indicates that the modem needs to generate the terrestrial frame and that
all non-inserted timeslots need to be filled with the appropriate idle code
based upon the terrestrial framing (T1 or E1).
Drop and Insert (D&I)
H–9
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