Avaya S8700 Maintenance Manual page 339

SYNC (Port-Network Synchronization)
Primary
PN
Figure 8-39. S8700 Media Server IP-Connected
The previous figure shows the third S8700 IP Connect system's PN without
public-network digital interface. A PN without public-network connectivity runs off
of its local IPSI circuit pack's Tone-Clock circuit.
Clock Synchronization
This section discusses synchronization with Stratum-4 clocking devices.
Stratum-4 Synchronization
An EPN can be configured with primary and secondary synchronization
references (DS1 or UDS1 Interface circuit packs) when using Stratum-4
synchronization. A primary reference must be used as the synchronization
reference and a secondary reference is optional:
If the primary synchronization reference is not providing a valid timing
signal, the system automatically switches to the secondary synchronization
reference.
If the primary synchronization reference is invalid and secondary reference
does not provide a valid timing signal or is not administered as a
synchronization reference, an IPSI's Tone-Clock circuit provides the EPN's
timing source.
If the system (PN for S8700 Media Server systems) is using the local
oscillator as the timing source (both the primary and secondary references
are providing invalid timing signals), should either the primary or secondary
reference becomes valid again, the system (PN for S8700 Media Server
systems) switches back to the primary or secondary source.
555-233-142
Public Switched Network
Primary
Secondary
IP Network
Secondary
PN
Sync Operation
Issue 1 May 2002
PN
8-1035