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804 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 757)

• “NTBK50 2.0 Mb PRI card” (page 867)

• “NTBK22 MISP card” (page 861)

• “NTRB21 DTI/PRI/DCH TMDI card” (page 953)

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 02.06 Standard

27 August 2008