Nortel Networks Circuit Card 311 User Manual
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NTAK10 2.0 Mb DTI card
The clock controller can operate in one of two modes: tracking or
non-tracking (also known as free-run).
The clock controller can operate in one of two modes: tracking or
non-tracking (also known as free-run). See
Tracking mode
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 are very near to being matched, the clock controller is locked
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 is
locked onto the reference once again.
If the incoming reference is unstable, the internal clock controller remains
continuously 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 is continually attempting to lock onto the signal. If slips are
occurring, however, it means that there is a problem with the clock controller
or the incoming line.
Free-run (non-tracking)
In free-run mode, the clock controller does not
synchronize on any source, it provides its own internal clock to the system.
This mode can be used when the , Cabinet system are used as a master
clock source for other systems in the network. Free-run mode is undesirable
if the CS 1000E, Cabinet system are intended to be a slave. It can occur,
however, when both the primary and secondary clock sources are lost due
to hardware faults or when invoked by using software commands.
Tracking mode
There are two stages to clock controller tracking:
•
tracking a reference, and
•
locked onto a reference.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311
01.04
Standard
Release 5.0
23 May 2008
Copyright © 2003-2008, Nortel Networks
.