Nortel Networks Circuit Card 311 User Manual
Page 904
904
NTAK20 Clock Controller daughterboard
ATTENTION
IMPORTANT!
Each Media Gateway that has a digital trunk must have a clock controller clocked
to an external reference clock.
If an IP Expansion multi-cabinet system is equipped with digital trunk cards, it is
mandatory that at least one trunk card is placed in the Main cabinet.
Note: Clocking slips can occur between systems that are clocked from
different COs, if the COs are not synchronized. The slips can degrade
voice quality.
The clock controller circuitry synchronizes the system to an external
reference clock and generates and distributes the clock to the system.
The system can function either as a slave to an external clock or as a
clocking master. The NTAK20AD version of the clock controller meets the
AT&T Stratum 3 and Bell Canada Node Category D specifications. The
NTAK20BD version meets CCITT Stratum 4 specifications.
The NTAK20 card performs the following functions:
•
phase lock to a reference, generation of the 10.24 Mhz system clock,
and distribution of the clock to the CPU through the backplane
•
accept one primary and one secondary reference
•
primary-to-secondary switchover and auto-recovery
•
chatter prevention due to repeated switching
•
error-burst detection and correction, holdover, and free running
capabilities
•
communication with software
•
jitter filtering
•
use of an algorithm to detect crystal aging and qualify clocking
information
The NTAK20 clock controller daughterboard mounts directly on the following
cards:
•
"NTAK09 1.5 Mb DTI/PRI card" (page 859)
•
"NTBK50 2.0 Mb PRI card" (page 967)
•
•
"NTRB21 DTI/PRI/DCH TMDI card" (page 1053)
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311
01.04
Standard
Release 5.0
23 May 2008
Copyright © 2003-2008, Nortel Networks
.