Nortel Networks 311

916 NTAK20Clock Controller daughterboard

An automatic switchover is initiated to the reference that recovers ﬁrst. If the

secondary recovers ﬁrst, then the clock controller tracks to the secondary;

however,it 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 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 ﬁrst. 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

and continues to do so 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 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.