NEC UNIVERGE SV9100 Features And Specifications page 351

If multiple BRIs exist but no PRI or T-1 EXTERNAL exists, the system chooses the first BRI that
synchronized with the carrier. In this example, the BRI in 04 synchronized with the carrier first and
became the PLO synchronization source.
Digital Trunk Clocking Example 7
In this scenario, the PRI was the clocking source until it went down. There are no other PRIs, T1
(Externals), or BRIs in the system. The GCD-CP10 now becomes the PLO synchronization source.
Digital Trunk Clocking Example 8
Guide to Feature Programming
Refer to the related features section for links to associated features.
Operation
Refer to the related features section for links to associated features.
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