Comtech EF Data SDM-9000 - Manual (Page 149)

SDM-9000 Satellite Modem Theory of Operation
Rev.4 5–21
5.5.3 Theory of Operation
The Interface PCB consists of the following basic subsections:
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TX terrestrial receivers (data and clock)
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RX terrestrial drivers (data and clock)
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TX overhead MUX (ESC optional)
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TX overhead receivers and processor
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RX overhead DEMUX (ESC optional)
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RX overhead processor and drivers
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Baseband loopback relays
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Interface loopback MUX
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Plesiochronous buffer (optional)
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Buffer clock MUX
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Modem fault/alarm relays
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Modem fault TTL outputs
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Backward alarms (ESC optional)
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Local monitor and control processor
Refer to Figure 5-6 for the interface block diagram.