SLM-3650 Satellite Modem
Revision 3
Options
MN/SLM3650.IOM
A–59
Master Site Option No. 2:
1. Set Configuration/Modulator/Modem Reference to INTERNAL.
2. Set Configuration/Interface/EXT-CLK Frequency to 10 MHz to INTERNAL.
3. Set Configuration/Interface/TX Clock Source and Buffer Clock to EXT Clock.
Note:
Input the 10 MHz clock at either the EXC (CP5) clock, unbalanced input of the
SMS-7000 data switch module, or balanced pins 7 and 8 of the switch module, V3.
This external clock input will go into the modem on pins 35 and 19 of the 50-pin
connector, located at the rear of the modem.
Slave Site:
1. Set Configuration/Interface/Loop Timing to ON.
2. Set Configuration/Interface /TX Clock Source to SCT (LOOP)
or TX Terrestrial, only if the user equipment can provide the proper slaved clock
to the modem.
Note:
SCT Internal changes to loop when Loop Timing is set to ON.
3. Set Configuration/Interface/Buffer Clock to RX (Satellite) “Buffer Bypass”.
A.1.9 G.703
Note:
If required, refer to Section A.3 for installation of the interface PCB.
G.703 data is either in AMI, B8ZS (8 zero) suppression, or HDB3 (3 zero) suppression
formats. There is not a coexisting clock that is on a separate line for G.703 data. The
clock is derived from the data stream within the modem and in the user equipment.
Loop timing, if desired, must occur in the customer equipment for the link to operate in
Master/Slave. The modem cannot do loop timing in G.703 operation because the modem
does not emit an ST signal for the Transmit Clock Source.
The modem can be placed in loop timing under EIA-422 or V.35 operation. Therefore, a
master/slave relationship easily occurs. This causes the receive clock to be placed on the ST
line to the terrestrial equipment. The customer equipment can then clock the transmit data to
the modem using the ST line that has been derived from the RX recovered clock.
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