Comtech EF Data SDM-300L3 - Manual (Page 260)

SDM-300L3 Satellite Modem Revision 1
Open Network Operations MN/SDM300L3.IOM
10–2
The receive data from the demodulator is input through the same interface loopback
device. The receive data is demultiplexed and synchronously descrambled by the
demultiplexer. The backward alarm is reported to the M&C and output by Form C relay
contact. The ESC is output by an EIA-232 driver. The terrestrial data output from the
demultiplexer is input to a plesiochronous buffer.
The front panel interface provides four clock selections clocking the data out of the
buffer:
• Internal Clock (SCT)
• RX Recovered Clock (RXCLK)
• External Reference Clock (EXT)
• High Stability Clock (HI STAB)
• TX Clock Dejittered (TXCLK)
If either RXCLK or EXT is selected and then fails, the interface automatically switches
to SCT as the source.
AIS is detected in the receive data and reported to the M&C.
The receive data and selected clock are translated to the levels of the selected baseband
interface and output through the baseband loopback relay.
The octet path is used for transferring a clock pulse to the distant end terrestrial
equipment. The clock pulse rate is the IBS data rate
÷ 8.
Refer to Figure 10-1 for a block diagram of the IBS interface.