Comtech EF Data OMS11 - Manual (Page 19)

Theory of Operation OMS11 1:1 Redundancy Switch
TM133 – Rev. 1.1 2-4
If Power Supply 1 and Power Supply 2 simultaneously fail, the switching circuitry in the OMS11
reverts back to Modem A, and the Switch Fault Relay switches to a faulted state. Modem B does
not receive buffered signals in this condition.
2.3.4 OMS11 Fault Relays
The OMS11 M&C Connector (J8) has Form-C contacts available that indicate modem online and
OMS11 Fault status. Refer to section for additional information.
2.4 Fault Detection
The OMS11 & OM20 work simultaneously to determine the status of all the components within
this system. The OMS11 & OM20 are capable of monitoring BUC and LNB redundancy system.
Faults detection is established by the OM20 and forwarded to the OMS11. Fault detection for a
redundant BUC system will be different based on whether the BUC Power is supplied by the
OM20 or if the BUC Power is supplied by an external power source. If the BUC power is supplied
externally, then the BUC must have Normally Closed Form C Fault contacts so the OMS11/OM20
can monitor the BUC fault status.
Fault detection with the OM20 supplying power to BUC:
• BUC Faults - OM20 uses internal fault detection circuitry to determine BUC status and
initiates a fault that is forwarded to the OMS11
• OM20 uses internal fault detection circuitry to determine LNB status and initiate fault
Fault detection with BUC power supplied externally:
• BUC must have Normally Closed Form C contacts in order for BUC fault detection to
work
• OM20 data cable CAR5902 or CAR5918 has an external connector that is used to
connect and monitor Form C Contacts from the BUC.
• OM20 uses internal fault detection circuitry to determine LNB status and initiate fault