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MAINTENANCE OF SWITCH UNITS
In this test the TSC inserts a pattern in all the 128 channels towards that
TIC and loops back at the TIC end and extract the pattern at TSC and
compares. If this test fails on all the TICs, then TSC could be suspected and a
diagnosis of TSC is required to be done. If the diagnosis passes, then TSM or
TSI or PSU could be indirectly contributing to the noise at the output of the
TSI or all the PCM links.
6.4.1.1.4.
IN CASE OF TICS BEING CONCENTRATED (Refer Fig. 6.3)
a)
CASE :
FAULT PROB. FOR MORE THAN ONE TIC IN THE
SAME PLANE IN A CHAIN
i. Following points are to be considered during concentration TIC
trouble-shooting :
•
When all the members of TIC concentration chains are O.K then
the chain can remain 'INS-ACT' or 'INS-SBY' mode. Criss-cross
configuration is not possible. If all the members of the chain are
not O.K, then the units which are O.K, will be 'INS- ACT' or
'INS-SBY' mode. Also, the plane with more no. of good units in
the chain will be INS-ACT and the other will be INS-SBY.
•
Whenever any unit in a chain is OOS-OPR the other units of
that copy will become OOS-EXT. This does not hold good if it is
thrown out by the system i.e. the unit is OOS-SYS.
For analysis purpose we are taking one chain say for example chain
3 which consists of TI09, TI10, TI11 and TI12. Copy-0 of these 4
TICs will be noted as copy-0 chain and copy-1 of these 4 TICs will
be called as copy-1 chain of TICs. Now, suppose a problem creeped
in any part of copy-0 chain, which we have to appendix. As soon as
problem occurred in copy-0 chain all the members of the TICs in
copy-1 chain will be instantly changed to 'INS-ACT' status. Due to
the fault, one or more than one TIC of the copy- 0 chain will go to
the 'OOS-SUS' (out of service suspect) status of which one or more
TIC unit may go to 'OOS-SYS' status, depending upon the fault.
Although an experienced maintenance person can locate the fault
easily by elimination method but to facilitate steady and methodical
approach for pinpointing the fault location following step-by-step
approach is suggested.
Only one observation, we have taken for reference is that due to
some problem copy-0 chain of TICs consisting of TI09-0, TI10-0,
TI11-0 and TI12-0 are not coming in service.
MAINTENANCE PROCEDURES
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