Alarm Threshold Recommendations For Digital Trunks; Clock Operation; Tracking Mode - Avaya CS 1000 Maintenance Manual

Alarm threshold recommendations for digital trunks

If a digital trunk is present in an IP expansion cabinet, link outages due to data network
performance degradation between the main cabinet and the expansion cabinet causes alarms
on the far end of the digital trunk. If link outages are frequent, alarm thresholds on the far end
may need to be increased to prevent the trunk from being placed in a state requiring manual
intervention to recover.

Clock operation

The system supports a single clock controller that can operate in one of two modes: tracking
or non-tracking (also known as free-run).

Tracking mode

In tracking mode, one or possibly two DTI/PRI cards supply a clock reference to a clock
controller daughterboard. When operating in tracking mode, one DTI/PRI is defined as the
primary reference source for clock synchronization, while the other is defined as the secondary
reference source (PREF and SREF in LD 73).
There are two stages to clock controller tracking:
• tracking a reference, and
• locked onto a reference.
When tracking a reference, the clock controller uses an algorithm to match its frequency to the
frequency of the incoming clock. When the frequencies nearly match, the clock controller locks
onto the reference. The clock controller makes small adjustments to its own frequency until
both the incoming and system frequencies correspond.
If the incoming clock reference is stable, the internal clock controller tracks it, locks onto it, and
matches frequencies exactly. Occasionally, however, environmental circumstances cause the
external or internal clocks to drift. When this happens, the internal clock controller briefly enters
the tracking stage. The green LED flashes momentarily until the clock controller locks onto the
reference again.
If the incoming reference is unstable, the internal clock controller remains in the tracking stage,
with the LED flashing green all the time. This condition does not present a problem, rather, it
shows that the clock controller continually attempts to lock onto the signal. If slips occur,
however, there is a problem with the clock controller or the incoming line.
ISDN Primary Rate Interface Maintenance
DTI/PRI maintenance tools
November 2011 119