Master/Slave G.703; Master/Slave X.21; Master/Master - Comtech EF Data SDM-309B Installation And Operation Manual

M&C and Interfaces
TX_CLOCK
BUF_CLK
RX_CLOCK

4.3.1.2 Master/Slave G.703

* There is no loop timing selection on board for G.703. It is assumed that any G.703
termination equipment will extract the clock from the satellite signal and turn it around
for retransmitting. The settings for the Master and Slave modems are the same as listed
above.

4.3.1.3 Master/Slave X.21

* Clock must be looped externally at slave end.
TX_CLOCK
BUF_CLK
RX_CLOCK
TX_CLOCK
BUFF_CLK
RX_CLOCK
4.3.1.4 Master/Slave External Station Clock
* Clock must be looped externally at slave end (For RS422 and V.35 see notes in
previous example).
RX_CLOCK
TX_CLOCK
BUFF_CLOCK
EXT_REF
TX_CLOCK
BUFF_CLK
RX_CLK
EXT_REF

4.3.2 Master/Master

This application is used where both earth stations have high stability clocks available and
the received data is to be clocked onto the local network.
The disadvantage of the master/master application is that the receive data will slip as the
clock will not be synchronized. The buffer if properly set up will ensure that the slips are
4-4–46
Modem Settings (Slave)
TX_TERR
SATELITE
NORMAL
Modem Settings (Master)
INT
INT
NORMAL
Modem Settings (Slave)
TX_TERR
SATELITE
NORMAL
Modem Settings (Master)
NORMAL
EXT_REF
EXT_REF
SET TO FREQUENCY OF STATION CLOCK
Modem Settings (Slave)
TX_TERR
SATELITE
NORMAL
N/A
SDM-309B Satellite Modem
MN/U-SDM309B Rev. #