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 sup ports 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 p rovides a holdover of at least 24
hours should both DS1 references fail. (After 24 hours, the Stratum 3 c lock still
provides service b ut its accuracy may be d egraded). The

Digital Synchronization

Network Plan (PUB 60110)

requires that the Stratum 3 clock have d uplicated
components.
The Stratum 3 clock can be c onfigured with only one DS1 input if one of the
Clock Input card s is removed. Also, the Stratum 3 clock c an free run (use its
internal clock without using DS1 inputs, if both Clock Input c ards are removed).
The recognition of the Stratum 3 clock itself as wel l as its alarm signals, is
supported only b y the TN780 Tone-Clock circuit pack. The TN780 Tone-Clock
circuit pack is also backwards-comp atible with the TN768 Tone-Clock circuit
pack. The Stratum 3 clock may b e connected to the PPN if the TN780 Tone-Clock
circuit pack(s) is present in that port network. The Stratum 3 clock shoul d never
be connected to an EPN.
The only operation that software can perfor m is a query of the alarm leads. The
only recovery action that c an be performed on a c atastrophic failure of the
Stratum 3 clock is using the loc al oscillator on the active TN780 Tone-Clock
circuit pack. Neith er software nor the TN780 Tone-Clock circuit pack can request
additional information ab out the health of the Stratum 3 clock other than the
information provided b y the alarm leads. Furthermore, neither the software nor
the TN780 Tone-Clock circuit pack can req uest that the external clock switc h
references, change c onfiguration, disable/enab le, 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 supp orted 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 provid es clock and alarm si gnals to the
TN780 Tone-Clock circuit pack(s). The reference DS1 facilities connec t directly to
the Stratum 3 clock for timing pur poses, 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