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DMD50 Universal Satellite Modem
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.1.3.1 Insert Terrestrial Frame Source
The Insert Terrestrial Frame Source selection tells the Modem from where the Insert Terrestrial
Frame is coming.
External:
Indicates that the terrestrial frame is to be input via the Insert Data In Port.
Internal:
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).
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.
H.1.4 D&I Sample Configurations and D&I Clock Setup Options
The following are several examples of how to configure the modem for D&I. Also, refer to Figures
3-14 through 3-17 for the D&I Clocking Setup Options Available.
Example 1:
Drop 512 Kbps from a T1 trunk, 3/4 Rate Viterbi
Insert 512 Kbps into a T1 trunk, 3/4 Rate Viterbi
Drop 512 Kbps from a T1 trunk, 3/4 Rate Viterbi
Under Interface:
Under TX Setup:
TM118 – Rev. 1.1
Set Tx Type according to your hardware configuration (example:
G703BT1B8ZS)
Set Tx Clock = SCTE
Under Tx D&I:
Set Drop Mode = T1-D4
Use SATCh TS edit capability to define desired mapping of
Satellite Channels to drop Terrestrial Slots
Use Map Copy to copy Tx Edit to Tx Active
Appendix H
H
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