Comtech EF Data SMS-758 - Manual (Page 76)

Theory of Operation SMS-758 Modem Protection Switch
4–16 MN/SMS758 Rev. 3
4.6.2 V.35 Interface Switch
The V.35 interface switch module switches all interface signals by relay. The prime
interface switch module (Figure 4-4) has two 34-pin female block connectors.
•
J1 (top) for terminal equipment is a DCE interface.
•
J2 (bottom) for prime modem is a DTE interface.
The backup interface switch module (Figure 4-5) has one 34-pin female block connector.
The backup modem (J1) is a DTE interface. The prime interface switch module can plug
into any interface switch module slot (A1 through A8) on the left side of the lower rear
panel. The backup interface switch module can plug into A9 or A10, on the right side.
The prime interface switch module can plug into any prime interface switch module slot
(A1 through A8) on the left side of the lower rear panel. The backup interface switch
module can plug into A9 or A10 (on the right side).
When the prime interface switch module (or the M:N switch itself) is powered down or
in the default position, all signals are routed between the terminal equipment and the
prime modem.
Modulator and/or demodulator signals can be independently switched to either of the two
backup modem interface switch modules, if the independent mod/demod firmware is
used. If modem switch firmware is used, then both the modulator and demodulator
switch to the backup when either the prime modulator or demodulator indicates a fault.
A buffered set of transmit clock (SCTE) and master clock (MC) signals is switched to
the “hot standby” backup modulator or demodulator, or to the offline prime modulator
and demodulator when a backup operation occurs.
The fault lines from the modem connector are routed through the interface switch
modules to the M&C.
4.6.2.1 Specification
Circuits Supported SD, SCT, SCTE, RD, SCR, MC, CTS, RTS, DSR, RLSD.
Switching Format Modulator and demodulator signals switched individually with dry
contacts.
Contact Arrangement Modulator signals: 8 poles
Demodulator signals: 8 poles