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Page Title: Voice Frequency Fault Isolation
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TM 11-5895-1012-10
the Technical Controller should reroute or restore in
ages must be recorded on the appropriate station logs,
accordance with established restoration priorities,
of the duration of the outage time or the
pending completion of repairs. Difficulties encount-
cause of the fault. Specific instructions for reporting
ered in obtaining a reroute path will be reported to the
of stations are contained in Standard Operating Proce-
appropriate DOCC and reroute instructions will be re-
dures published by DCA and ACC. Trouble reports
(work orders) must be prepared for each equipment or
circuit failure. This work order will notify mainte-
4-29. Voice Frequency Fault Isolation
nance of the faulty or sub-standard equipment- Only
When a Technical Controller discovers that a circuit or
by strict adherence to this procedure can proper rec-
a multiplex group is not operating within established
ords be maintained. Prompt, efficient repair of faulty
parameters, in-service monitoring tests should be per-
equipment often depends upon the completeness and
formed in accordance with established station proce-
accuracy of these symptoms described on the written
dures. This will help determine whether a single chan-
nel, an entire group or supergroup, or the baseband is
d. Catastrophic Failure. Normally, the Technical
affected. In addition, whether the fault is located with-
Controllers keep DCA and ACC informed of anticipat-
in the station multiplex or line conditioning equip
ed, imminent, or existing service failures or degraded
ment. Time is important. The goal is to locate and cor-
conditions which are beyond the local capability to re-
rect the fault before the users service becomes unuse-
store within a tolerable delay or outage time period. In
an exceptional case, a catastrophic failure condition
a. In coordination with the distant station(s) and the
may be encountered in which the alarm indicator dis-
appropriate control office(s), using available order-
play may depict a number of simultaneous alarms or
wires, selective elimination of each portion of the cir-
provide an indication of a second major alarm within
cuit may be used to locate the fault area. In-station
the same station before the first alarm has been
monitoring procedures will locate the fault specifically
cleared. In these cases, DCA or ACC may provide alter-
enough to permit the Technical Controller to modify
nate routing instructions, or other solutions, as appli-
established fault isolation procedures and attack the
problem directly, either by substituting for the faulty
4-28. Fault Isolation Procedures
item, or by making a patching substitution. Then
through the use of out-of-service testing procedures, or
The guidelines contained in paragraphs 4-29 through
the in-station test and alignment procdures, correct
4-34 are for use in preparing local procedures and in
the problem.
determining the location of the equipment or media
which is causing signal degradation. It may not be nec-
b. Keep in mind that the fault isolation procedures
essary to take each step in the order listed. Depending
established, serve only as a guide for efficient techni-
upon the trouble indications, it is possible that some
cal control operations and do not represent a rigid se-
steps may be taken in different sequence, combined
quence of steps which must be followed to solve a prob-
with other steps, or even eliminated completely. A
lem. The Technical Controller should by-pass any un-
Technical Controller's first questions, when a problem
necessary steps in order to quickly locate the fault and
is recognized, should be "Does the problem affect only
restore normal service.
a single circuit or channel, or the entire group or super-
4-30. Single Voice Frequency Channel
group?" and then, "Is the circuit, group or supergroup
meeting the standards through my station?" The Tech-
nical Controller must then take the actions necessary
When it is determined that a single voice channel of a
to answer those questions. All steps will be taken in
voice frequency group is unuseable or deteriorated, the
complete coordination with the other stations through
station Technical Controller will take the following ac-
which the signal is routed, and with the local mainte-
nance activity.
a. Coordinate with the distant station Technical
a. Fault isolation should proceed from the point of
Controller to transfer service to a spare channel, or
fault recognition toward the signal source to the point
preempt a lower priority user if required. If a low pri-
where the fault exists. Results of in-station checks will
ority user is preempted, have the distant station Tech-
be completely coordinated with the other concerned
nical Controller notify the low priority user of the pre-
TCF's and the trouble corrected at the source. Adjust
ments will not be made at intermediate points to com-
b. Request the distant station Technical Controller
pensate for a problem generated at some other point in
to send a test signal on the faulty channel in accord-
the circuit or system.
ance with the appropriate out-of-service test procedure
b. In the event a known fault cannot be corrected
after the traffic signal has been moved to another
within a reasonable amount of time (i.e., 10 minutes),

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