Specifications

X723-300151 5-18 Issue 2
Change-over Operation
The decision to switch or not to switch will be made on the basis of the
table below when the delay time expires. Faults which occur and clear
within the switch over delay time will not be considered for the purposes
of the decision table.
ACTIVE STREAM STANDBY STREAM
ACTION
No fault No fault
None
Low error rate No fault
Switch
Low error rate Any fault
None
Any fault except low
error rate
Low error rate
Switch
Any fault except low
error rate
Any fault except low
error rate
None
Faults
During failure conditions, PCM alarm responses will be set and reported
as for normal PCM operation of the LIU. If PCM Line 1 is selected, the
following status message will be generated in the active fault list:-
'Path A selected'.
Similarly if PCM Line 2 is selected, the following status message will be
generated:-
'Path B selected'.
These 'faults' are used as information markers, and have a network fault
level of zero and cause no alarm relay or LED operation.
Fault Persistency
One fault may cause the change over timer to start running, but that
same fault need not be active when change-over occurs, another fault may
take its place, e.g. PCM loss occurs and is then replaced by AIS. Only
when all relevant faults have been cleared will the timer be reset.
5) Error
The threshold for the low error rate detector may be individually set to
10
-4
, 10
-5
or 10
-6
for line 1 and line 2. This does not affect detection of 10
-3
which is required for line service monitoring. If the threshold is exceeded,
then the low error rate fault is generated.