Comtech EF Data SDM-2020, Installation And Operation Manual

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Data Interfaces SDM-2020 Satellite Demodulator
A–50 Rev.3
A.6.5 Receive Doppler/Plesiochronous Buffer Specifications
A.6.5.1 Buffer Size
The operator can set the buffer size, ranging from 2 milliseconds to 32 milliseconds, in
2 millisecond steps. There is also a buffer bypass selection, buffer size of 0 milliseconds.
A.6.5.2 Frame Structures
The unit provides programmable plesiochronous buffer slips.
Frame structures provided according to data rate:
•
1544 kbit/s - None or G.704
•
2048 kbit/s - None or G.704
•
6312 kbit/s - None, G.704, G.743, or G.747
•
8448 kbit/s - None, G.704, G.742, or G.745
•
32064 kbit/s - None or G.752
•
34368 kbit/s - None, G.751, or G.753
•
44736 kbit/s - None, G.752
•
51840 kbit/s - None or STS-1
A.6.5.3 Buffer Clock Sources
The unit shall provide for buffer clock source selections.
Source selections:
•
Internal
•
Transmit terrestrial
•
External Reference
•
RX satellite
A.6.5.4 Buffer Clock Backup
In the event of failure of the selected buffer clock the unit automatically selects the RX
satellite clock as the backup.