DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126
Issue 4
June 1999
Maintenance Object Repair Procedures
9-1536STRAT-3 (Stratum 3 Clock)
9
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. The Release 5r system supports both
Stratum 3 and Stratum 4 operations. Refer to “SYNC (Synchronization)” for
details on Stratum 4 operation.
A Stratum 3 clock derives its timing from two DS1 references connected to a
Stratum 3 or better 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 Stratum 3 clock can be configured with only one DS1 input if one of the
Clock Input cards is removed. Also, the Stratum 3 clock can free run (use its
internal clock without using DS1 inputs, if both Clock Input cards are removed).
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 the PPN if the TN780 Tone-Clock
circuit pack(s) is present in that port network. The Stratum 3 clock should never
be connected to an EPN.
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 using 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, and so forth.
In the system, the Stratum 3 clock has been implemented as an external which
follows the specification in PUB 60110 for Stratum 3. The only external Stratum 3
clock that is supported is the Telecom Solutions Digital Clock Distributor
™ for
Customer Premise Timing (DCD-CPT) Stratum 3 clock. Figure 9-90
shows how
the Stratum 3 hardware configuration provides clock and alarm signals to the
TN780 Tone-Clock circuit pack(s). The reference DS1 facilities connect directly to
the Stratum 3 clock for timing purposes, but the DS1 data may be routed into the
MO Name (in
Alarm Log) Alarm Level Initial Command to Run Full Name of MO
STRAT-3 MAJOR test synchronization Stratum 3 Clock
STRAT-3 MINOR test synchronization Stratum 3 Clock
