Comtech EF Data SMS-758 - Manual (Page 70)

Theory of Operation SMS-758 Modem Protection Switch
4–10 MN/SMS758 Rev. 3
4.4 Fault Interface Specification
This section defines the protocol and format structure for monitoring the fault status
interface of the switch.
The relay-remote/fault rear panel connector (J6) provides interface for fault status
information. (See Section 2.4.5 for connector location and pin-out information.)
Three non-latching relays with form C contacts show:
•
Controller status
•
M:N status
•
Demodulator signal status
These contacts report summary status. To determine the exact fault, the user must make
further inquiry, as described in Section 3.2.4.
4.4.1 Controller fault
A controller fault is a catastrophic failure that renders the switch non-functional. A timer
on the M&C periodically sets a monostable multivibrator which controls the fault relay.
The controller fault relay NC and COM contacts close when one of the following occurs:
•
No power is applied to the switch.
•
M&C fails to set the monostable.
During normal operation (when no fault occurs), the relay NC and COM contacts are
open, and the NO and COM contacts are closed.
4.4.2 M:N Fault
An M:N fault is any failure of backup operation, communication, configuration, and/or
setup that may (or may not) render the switch non-functional.
During normal operation or when power is OFF, the relay is de-energized (COM to NC).
When any failure occurs, the relay energizes (COM to NO). It remains energized until
the failure is eliminated.