Nortel Networks 311

Functional description 915

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.

Switchover occurs in the case of referencedegradation 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 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 tracksto 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 overto the pr imary when the primary recovers. If the primary

recovers ﬁrst, the clock controller tracksto the primar y 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 secondar y 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 ��rst. If the primary recovers ﬁrst, the clock controller tracks to the

primary, butswitches 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.

Toprevent chatter due to repeated automatic switching between primary

and secondary reference sources, a time-out mechanism of at least 10

seconds is implemented.

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 if that is within

speciﬁcations. On failure (both out of speciﬁcation), the clock controller

enters the HOLDOVER mode and continuously monitors both references.

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 01.04 Standard

Release 5.0 23May 2008