Nortel Communication Server 1000 Maintenance Manual page 80

80 Clock controller maintenance
Figure 14
Clock controller primary and secondary tracking
Free run (non-tracking) mode
The clock synchronization for a PRI loop can operate in free-run mode if
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Reference clock errors
System software checks every 0-15 minutes (programmable) to see if a
clock-controller or reference-clock error has occurred.
In tracking mode, at any one time, there is one active clock controller
which is tracking on one reference clock. If a clock-controller error is
detected, the system switches to the backup clock controller, without
affecting which reference clock is being tracked.
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the loop is not defined as the primary or secondary clock reference
the primary and secondary references are disabled
the primary and secondary references are in local alarm
Nortel Communication Server 1000
ISDN Primary Rate Interface Maintenance
NN43001-717 03.01
11 May 2009