Avaya Nortel Communication Server 1000 Reference page 590

NTDW12AAE5 Universal Clock Controller daughter board
EIA/CCITT compliance
The clock controller complies with 1.5 Mb EIA Stratum 3ND, 2.0 Mb CCITT or 2.56 Mb basic
rate. The differences between these requirements mainly affect PLL pull in range. Stratum 4
conforms to international markets (2.0 Mb) while Stratum 3 conforms to North American
markets (1.5 Mb).
Monitoring references
The primary and secondary synchronization references are continuously monitored to provide
autorecovery.
Reference switchover
Switchover may occur in the case of reference degradation or loss of signal. When
performance of the reference degrades to a point where the system clock is no longer allowed
to follow the timing signal, then the reference is out of specification. If the reference being used
is out of specification and the other reference is still within specification, an automatic
switchover is initiated without software intervention. If both references are out of specification,
the clock controller provides holdover.
Autorecovery and chatter
If the command "track to primary" is given, the clock controller tracks to the primary reference
and continuously monitors the quality of both primary and secondary references. If the primary
goes out of specification, the clock controller automatically tracks to secondary when the
secondary is within specifications. On failure (both out of specification), the clock controller
enters the HOLDOVER mode and continuously monitors both references. An automatic
switchover is initiated to the reference that recovers first. If the secondary recovers first, then
the clock controller tracks to the secondary, then switches over to the primary when the primary
recovers. If the primary recovers first, the clock controller tracks to the primary and continues
to do so even if the secondary recovers.
If the command "track to secondary" is given, the clock controller tracks to the secondary
reference and continuously monitors the quality of both primary and secondary references. If
the secondary goes out of specification, the clock controller automatically tracks to primary
provided that is within specifications. On failure (both out of specification), the clock controller
enters the HOLDOVER mode and continuously monitors both references. An automatic
switchover is initiated to the reference that recovers first. If the primary recovers first, the clock
controller tracks to the primary, but switches over to the secondary when the secondary
recovers. If the secondary recovers first, the clock controller tracks to the secondary even if
the primary recovers.
590 Circuit Card Reference
Comments? infodev@avaya.com
July 2011