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Basic Rate Interface (BRI) Feature

Description: Clock Switching

When the primary clock source is not able to provide the system clock, the secondary clock source is used, if it exists and is capable of providing the system clock. If the secondary clock source is incapable of providing the system clock, the tertiary clock source is used. If none of these is capable of providing the system clock, the system selects a system clock.

The system searches 800 NI-BRI and 100D/100R/100 DCD modules for a clock source, starting from the first module in the system and ending with the last module. The clock is chosen with the following order of preference:

1. The loop clock source on an 800 NI-BRI or 100D/100R/100 DCD module.
   
   
2. The local clock source on an 800 NI-BRI or 100D/100R/100 DCD module.
   
   
3. The local clock source on the processor module.

Refer to the Network Reference for information on clock switching for private networks (Hybrid/PBX mode only).

Topics
	Description
	Terminology Clock Synchronization Clock Switching Timers and Counters Call Processing
	At a Glance
	Considerations & Constraints
	System Programming
	Feature Interactions