Maintenance Object Repair Procedures
555-233-123
10-1784 Issue 4 May 2002
High Reliability Option
Systems with the High Reliability Option (duplicated SPE, simplex PNC) have one
Tone-Clock circuit pack in each PPN control carrier, A and B. One Tone-Clock
circuit pack will be actively generating system clock signals for PPN components,
while the other will be in standby mode, ready to take over in the event of a
Tone-Clock interchange. Similarly, one Tone-Clock circuit pack will be actively
providing system tones for the PPN, while the other will be in standby mode.
Normally, the same Tone-Clock circuit pack will be active for both tones and clock
signals, but these responsibilities may be divided if neither circuit pack is able to
perform both functions. The status port-network command will indicate which
Tone-Clock circuit pack is actively performing each function.
For systems using the TN2182 Tone-Clock-Detector circuit pack, tone generation
and clock generation behaves the same as other clock boards with one being
active and one being standby. But the tone detector ports (ETR-PTs) of the
TN2182 are always considered available and in-service regardless of the
active/standby state of the tones or clock for a specific circuit pack.
EPN Tone-Clock circuit pack configuration is the same as for the Standard
Reliability Option. Each EPN Tone-Clock circuit pack will be active for both tones
and clock signals for its port network.
Critical Reliability Option
Systems with the Critical Reliability Option (SPE duplication and PNC duplication)
have two Tone-Clock circuit packs associated with the PPN, as in the High
Reliability Option case, and two more Tone-Clock circuit packs for each EPN. For
the EPN, these are in carriers A and B. As in the previous case, one Tone-Clock in
each Port Network is active, supplying system clocks and tones, and the other is
in standby mode.
Tone-Clock Interchange Strategy
The Tone-Clock circuit pack interchanges are controlled both by manual
intervention and by maintenance software strategies.
The manual interchange strategy for Tone-Clock circuit packs differs slightly
between the PPN and any EPNs on a system.
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