Comtech EF Data SDM-9000, Installation And Operation Manual

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SDM-9000 Satellite Modem Theory of Operation
Rev.4 5–27
5.5.3.3.2 Interface Loopback
Interface loopback provides loopback at the interface between the interface module and
the modulator/demodulator. The near end equipment loops through the interface module
and the far end equipment loops through the modulator/demodulator. Refer to Figure 5-8
for a block diagram.
TX DATA/CLOCK
TERRESTRIAL
RX DATA/CLOCK
TX DATA
RX DATA
MODULATOR
DATA
DEMODULATOR
DATA
MODULATOR
MODULE
DEMODULATOR
MODULE
INTERFACE
MODULE
TX IF OUT
RX IF IN
INTERFACE
LOOPBACK
MUX
DATA/CLOCK
Figure 5-8. Interface Loopback Block Diagram
5.5.3.4 Engineering Service Channel (ESC)
The ESC includes the following features:
•
Two full duplex audio channels or one 64 kbit/s data channel
•
A full duplex 8 kbit/s data stream
•
Four backward alarms (described in IESS-308)