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OM20 Universal Outdoor Modem
E.6.2 Operational Network Specification
The Network Specification of the Modem often determines which additional menus and displays
are available for use by the operator. The D&I Mode-specific menus will not be displayed unless
the Network Spec. of the modem is set to D&I. Therefore, the next step in configuring the modem
should be to set the Network Spec. to D&I. At this point, the D&I specific menus in the Interface
section will become available and will remain available until the Network Spec. of the modem is
changed to something other than D&I. When the Network Spec. is changed to something other
than D&I, the D&I specific menus will automatically disappear.
E.6.3 Terrestrial Framing - Drop Mode/Insert Mode
The Drop Mode Selection and the Insert Mode Selection identify the Terrestrial Data-Framing
Format. As previously mentioned, their selection is influenced by the Modulator and Demodulator
Data Rates, and trying to select a T1 Type Framing Format with a data rate of 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.
E.6.3.1
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
(Internally looped to the DDO 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.
TM116 – Rev. 1.2
Appendix E
E-
9
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