Paradyne 8779 User Manual page 112

A. Configuration Options
When a system clock source fails or is misconfigured, an alarm is reported.
Secondary clock failures are not reported unless the primary clock has also failed.
When the primary clock fails, clocking is switched to the secondary clock source, if
available. If a secondary clock is not available, the clock switches to secondary
holdover mode. In holdover mode, the system attempts to generate timing which is
consistent with the last clock reference. A switch is made back to the primary clock
when it becomes available. Holdover mode is meant to be used for short durations
while network synchronization is temporarily disrupted. The switch back to
primary/secondary clock is made when they become available again.
Figure A-1, System
Figure A-1.
Figure A-2, System Clock Configuration
configurations.
A-16
Timing, shows clocking in an LTU.
DSL
Framer
Transceiver
System Timing
System Timing
May 2002
Framer
Cross-Connect
System
Timing
Module
DSX-1/G.703 Port
Internal Oscillator
Examples, shows sample system clock
DSX-1/
G.703
Driver
99-16627
8700-A2-GB20-40