Symmetricom SSU-2000 User Manual page 165

The Input module maintains a count of the number of consecutive seconds in which
the input signal for each port is free of each type of error. This clear count must
exceed a user-set limit before the input signal is no longer in episode. Refer to
Changing Factory
count.
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. The default is 10 seconds.
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, the system takes appropriate action according to the severity level
assigned to the alarm.
LOS Phase Considerations
Phase reading not valid when in episode
Zero phase reading when episode ends
If signal returns before the port goes into episode, normalize subsequent phase
measurements to show continuous phase numbers before and after the loss of
signal.
Others
Phase reading valid
Hierarchy of Alarm Signals
LOS
AIS
OOF
BPV/CRC
The Input module does not report alarms below the level of an active alarm.
Cesium Fault
Facilitates compatibility with older Hewlett Packard units
Only valid if port one is configured to receive an unframed input signal
12713020-002-2 Revision F.01 – January 2007
Defaults, on page 114, for more information on setting the clear
Chapter 7 Input Module Reference Data
1-Port and 3-Port E1 Input Modules
SSU-2000 User's Guide 165