Symmetricom SSU-2000e User Manual page 177

Input Signal PLL Unlocked
– Report event message and perform other actions as required by severity
– Fault port, regardless of severity
– Monitor PLL for recovery
Phase Measurement Circuitry Fault
– Report event message and perform any other required actions
– Fault Port
– Monitor phase hardware for recovery
Handling Input Signal Faults
The following alarms are caused by problems with the incoming input signal's
formatting or content:
Errors Tracked:
– Framed signals: LOS, AIS, OOF, BPV and CRC
– Unframed signals: LOS
Error and Clear Counters
The Input module maintains a count of the number of consecutive errored seconds
for each error type for each port. Once this error count exceeds a user-set limit, the
input signal which has experienced the errors is said to be in episode.
The Input module maintains a count of the number of consecutive seconds in which
the input signal for each port was free of each type of error. This clear count must
exceed a user-set limit before the input signal is no longer in episode.
Handling Input Signal Faults
For LOS (loss of signal) and before going into episode:
Coast over brief occurrences of LOS, reporting the last known good phase
measurements for the port until signal returns or the signal goes into episode.
The duration of a brief occurrence of LOS is defined by the value of the error
count for LOS.
Once in episode:
Log LOS alarm, taking appropriate action per the assigned severity level
Invalidate current phase measurements
Others (AIS, BPV, CRC, and OOF)
Once in episode, take appropriate action according to the severity level assigned
to the alarm
12713140-002-2 Revision E – October 2006
Chapter 7 Input Module Reference Data
1-Port and 3-Port DS1 Input Modules
SSU-2000e User's Guide 177