User Guide

DEFINITY Enterprise Communications Server Release 5
Maintenance and Test for R5vs/si
555-230-123
Issue 1
April 1997
Maintenance Object Repair Procedures
Page 10-1294STRAT-3 (Stratum 3 Clock)]
10
10
STRAT-3 (Stratum 3 Clock)]
The Digital Synchronization Network Plan (PUB 60110) specifies a hierarchy of
synchronization nodes consisting of strata 1 to 4, where the sole Stratum 1 clock
in the network is the most accurate. DEFINITY supports both Stratum 3 and
Stratum 4 operations. Refer to SYNC (Synchronization) Maintenance
documentation for details on Stratum 4 operation.
A Stratum 3 clock derives its timing from two DS1 references that are connected
to a Stratum 3 or better (that is, lower stratum) source. The Stratum 3 clock
provides a holdover of at least 24 hours should both DS1 references fail. (After 24
hours, the Stratum 3 clock still provides service but its accuracy may be
degraded). The
Digital Synchronization Network Plan (PUB 60110) requires that
the Stratum 3 clock have duplicated components.
The recognition of the Stratum 3 clock itself as well as its alarm signals, is
supported only by the TN780 Tone-Clock circuit pack. The TN780 Tone-Clock
circuit pack is also backwards-compatible with the TN768 Tone-Clock circuit
pack.
The Stratum 3 clock may be connected to either the PPN or an EPN if the TN780
Tone-Clock circuit pack(s) is present in that port network. However, for reliability,
it is recommended that the clock be connected to the PPN. Refer to
DEFINITY
Communications System Generic 3 Implementation
, 555-230-653 for details on
how to move the Stratum 3 clock between port networks.
The only operation that software can perform is a query of the alarm leads. The
only recovery action that can be performed on a catastrophic failure of the
Stratum 3 clock is the utilization of the local oscillator on the Active TN780
Tone-Clock circuit pack. Neither software nor the TN780 Tone-Clock circuit pack
can request additional information about the health of the Stratum 3 clock other
than the information provided by the alarm leads. Furthermore, neither the
software nor the TN780 Tone-Clock circuit pack can request that the external
clock switch references, change configuration, disable/enable, initialize, etc.
In G3iV1.1-286 and G3iV2-386, the Stratum 3 clock has been implemented as an
external that follows the specification in PUB 60110 for Stratum 3. Figure 10-85
shows how the Stratum 3 hardware configuration provides clock and alarm
signals to the TN780 Tone-Clock circuit pack(s). The reference DS1 facilities are
MO Name As
It Appears in
Alarm Log
Alarm
Level
Initial System
Technician Command
to Run Full Name of MO
STRAT-3 MAJOR test synchronization Stratum 3 Clock
STRAT-3 MINOR test synchronization Stratum 3 Clock
STRAT-3 WARNING test synchronization Stratum 3 Clock