Avaya Definity SI Maintenance Manual page 212

Reliability Systems: A Maintenance Aid
Tone-Clock Circuit Pack Duplication
For more information about the Tone-Clock circuit packs see TONE-BD in
Chapter 10, ''Maintenance Object Repair
The TONE-BD (Tone-Clock) MO functionality is made up of the TONE-PT (Tone
Generator) and the TDM-CLK (TDM Bus Clock). The Tone Generator provides all
tones required by the system; the TDM Bus Clock provides synchronization for
the TDM Bus and aids in monitoring and selection of SYNC (Synchronization)
references.
Each High or Critical Reliability system provides two Tone-Clock circuit packs. In
this configuration, a failed Tone-Clock circuit pack is switched off-line and an
operational circuit pack is put on-line. Duplication Interface A selects the Active
Tone-Clock circuit pack by driving the Tone-Clock Select lead. The selection of the
Active Tone-Clock circuit pack is independent of the selection of the Active SPE.
Time Division Multiplexing Bus Duplication
The TDM Bus is composed of two separate, independent buses called bus A and
bus B. The first five time slots of both buses are reserved for communication
between the SPE and port circuit packs. These time slots are known as the
control channel. The control channel is a vital component and must be operational
for the system to provide meaningful customer voice and data services. In
addition to the control channel time slots, several other time slots are reserved for
system use. These additional time slots are for the standard tones. The standard
tones include the dial tone and the touch tones.
The ability to move the control channel and tones from a defective TDM Bus to an
operational TDM Bus is a key component of a highly-available system. The
system can detect transmission errors on the control channel, errors can be
diagnosed, and corrective actions can be taken when necessary. If a bus is found
to be defective, it is taken out-of-service. All existing calls on the out-of-service
bus are maintained, but no new calls are assigned to the out-of-service bus.
In addition to the system software's ability to detect a defective bus and perform a
TDM Bus switch, the user also has the ability to specify if and when a scheduled
control channel switch is to be performed.
6-8 Issue 4 May 2002
Procedures''.
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