Nortel-networks Circuit Card Manuel d'utilisateur télécharger pdf (Page 355)

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NT5D97 Dual-port DTI2/PRI2 card Page 355 of 906

Circuit Card Description and Installation

system switches to the back-up clock controller, without affecting which

reference clock is being tracked.

A reference-clock error occurs when there is a problem with the clock driver

or with the reference clock at the far end. If the clock controller detects a

reference-clock error, the reference clocks are switched.

Automatic clock recovery

A command for automatic clock recovery can be selected in LD 60 with the

command EREF.

A DDP2 loop is disabled when it enters a local-alarm condition. If the local

alarm is cleared, the loop is enabled automatically. When the loop is enabled,

clock tracking is restored in the following conditions:

• If the loop is assigned as the primary reference clock but the clock

controller is tracking on the secondary reference or in free-run mode, it

is restored to tracking on primary.

• If the loop is assigned as the secondary reference clock but the clock

controller is in free-run mode, it is restored to tracking on secondary.

• If the clock check indicates the switch is in free-run mode:

— Tracking is restored to the primary reference clock if defined.

— If the primary reference is disabled or in local alarm, tracking is

restored to the secondary reference clock if defined.

Note: If the system is put into free-run mode by the craftsperson, it

resumes tracking on a reference clock unless the clock-switching option

is disabled (LD 60, command MREF), or the reference clock is

“undefined” in the database.

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Nortel-networks Circuit Card Manuel d'utilisateur Page 355

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