Comtech EF Data SMS-758 - Manual (Page 74)

Theory of Operation SMS-758 Modem Protection Switch
4–14 MN/SMS758 Rev. 3
TRANSMIT CLOCK
TRANSMIT DATA
RECEIVE DATA
RECEIVE EXTERNAL
REFERENCE CLOCK
RECEIVE CLOCK
TX S/B TX
TX
PRIME C/U
DATA I/O
RX
TERRESTRIAL
DATA I/O
RX
DATA PATH
SELECTION
RX S/B
RX
NOTE: THE RELAYS ARE SHOWN IN THE NON-ENERGIZED
POSITION CONNECTING THE TERRESTRIAL DATA AND
PRIME MODEM CONNECTORS TOGETHER. STANDBY (S/B)
SIGNALS ARE ROUTED TO THE OFFLINE BACKUP MODEM.
TRANSMIT CLOCK
RECEIVE DATA
RECEIVE CLOCK
TRANSMIT DATA
RECEIVE EXTERNAL
REFERENCE CLOCK
MOD AND DEMOD FAULTS
DATA SWITCH
MOTHERBOARD
INSTRUCTION
DECODER
MOD RELAYS
DEMOD RELAYS
FAULTS
TRANSMIT CLOCK
TRANSMIT DATA
RECEIVE DATA
RECEIVE CLOCK
RECEIVE EXTERNAL
REFERENCE CLOCK
Figure 4-2. Prime RS-422/449 and MIL-STD-188-114/RS-449 Interface Switch