Symmetricom SSU-2000e User Manual page 169

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 the input 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
User can select high or low logic level as alarmed
If the hardware indicates that the cesium fault level matches the alarmed setting,
log an AIS alarm against port 1
Clear the alarm when the hardware's cesium fault level no longer matches the
alarmed level
12713140-002-2 Revision E – October 2006
Chapter 7 Input Module Reference Data
1-Port and 3-Port E1 Input Modules
SSU-2000e User's Guide 169