DEFINITY ECS Release 8.2 Maintenance for R8.2csi
555-233-119 Issue 1
April 2000
Maintenance Objects
3-1004SYNC (Synchronization)
3
Synchronization Troubleshooting
For Stratum 4 operation, major and minor alarms indic ate that there is a problem
with the system synchronization references. These alarms are resolved when the
alarmed synchronization referenc e is restored.
The status synchronization and display synchronization commands are used
to determine the current system sync hronization reference and the primary and
secondary references that are administered respectively.
Other commands associated with Synchronization Maintenance are disable
synchronization-switch and enable synchronization-switch. These
commands are used to d isable the ability of Synchronization Maintena nce to
switch between synchroniz ation references and to enable this switc hing ability,
respectively. The set synchronization command is executed only after
synchronization has been d isabled and is used to manually switch to a spec ific
synchronization reference. This command is useful to diagnose synchronization
problems by forcin g a specific referenc e (DS1 or Tone-Clock) to be the system
synchronization reference to deter mine if a specific referenc e is providing a valid
timing signal. For Stratum 3 operation, only a TN780 Tone-Clock circuit pac k may
be specified . To switch synchronization to the Stratum 3 clock, use the enable
synchronization-switch command after verifying that the Stratum 3 cloc k is
wired correctl y.
The system synchronization planner must avoid creating a

timing loop

when
administering the primar y and secondary sync hronization references in a
system. A timing loop exists whenever a s ystem receives timing from another
system whose timing reference is direc tly or indirectly derived from itself. Timing
loops can lead to loss of digital data betwe en systems that are exchanging d ata
with any system within the loop. An invalid timing signal is also generated b y any
system within the loop, thus prop agating the invalid timing signal to any
system(s) using a system within the loop as a synchronization reference. Fig ure
3-41 shows a timing loop and a correct distribution of timing between the
systems.