Comtech EF Data SMS-458B - Manual (Page 75)

SMS-458B Modem Protection Switch Revision 2
Theory of Operation MN/SMS458B.IOM
4–15
TRANSMIT ESC
RECEIVE ESC
RECEIVE EXTERNAL
REFERENCE CLOCK
TX
PRIME C/U
DATA I/O
RX
TERRESTRIAL
DATA I/O
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.
RECEIVE ESC
TRANSMIT ESC
MOD AND DEMOD FAULTS
DATA SWITCH
MOTHERBOARD
INSTRUCTION
DECODER
TX RELAYS
RX RELAYS
RECEIVE EXTERNAL
REFERENCE CLOCK
FAULTS
TRANSMIT ESC
RECEIVE ESC
RECEIVE EXTERNAL
REFERENCE CLOCK
J5
J1
J2
TRANSMIT DATA
TX DATA
RX DATA
RECEIVE DATA
J6
J4
J3 TX DATA
RX DATA
Figure 4-2. Prime IDR/G.703 Interface Switch
BACK/UP C/U
DATA I/O DATA SWITCH
MOTHERBOARD
TRANSMIT ESC
RECEIVE ESC
RECEIVE EXTERNAL REFERENCE CLOCK
MOD AND DEMOD FAULTS
TRANSMIT DATA
RECEIVE DATA
Figure 4-3. Backup IDR/G.703 Interface Switch