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Page Title: Examples of Voice Channel Fault Isolation Procedures
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TM 11-5895-878-14&P
temporarily by patching, and high priority circuits are
which includes his mux system. He should check other
disrupted, he should request authority from the CCOC or
circuits in the same mux group to determine if the fault
DCA to preempt lower priority circuits.
is confined to the circuit under test. If an entire group
proves to be at fault, he should call in maintenance
(2) In the event that the malfunction can be
personnel to check multiplex group equipment, inform
cleared only by corrective maintenance, he should
the responsible technical controller and prepare to
request that the distant technical controller(s) involved
coordinate with the station at the other end of the faulty
hold traffic, pending completion of the repairs, and
link. Group patching may be required. If only the circuit
ensure that all users of the affected circuits are advised
under test is faulty, the responsible technical controller
of the temporary disruption of traffic.
should be informed that this station is not the fault
(3) If the fault occurred at a distant station, he
source and the isolation procedure should be continued
should assist the distant technical controller in the
at points closer to the signal source. He should also
restoration of the circuits, as required.
request the station maintenance personnel to check the
d. Baseband. When it has been determined that
channel modem associated with the subscriber circuit.
an entire baseband is unserviceable, the station
(2) If noise was not encountered, the fault
technical controller should:
then lies in the mux and radio link between the patch
(1) Request that station microwave personnel
bay at this site and the distant site.  This can be
check the serviceability of the radio equipment assigned
assumed since this distant station would have previously
to the link, and the serviceability of the associated
established that the fault was not in his TCF and the
multiplex terminal equipment.
local technical controller has established that the fault is
(2) In the event that the malfunction can be
in his direction. The station responsible for the circuit
cleared only by corrective maintenance, he should
should be informed, maintenance people should be
immediately contact the (CCOC and DCA and request
requested to check the channel modem equipment, and
rerouting instructions for any high priority circuits that
the controller should prepare to patch around the faulty
may be involved.
(3) If the fault occurred at a distant station, he
(3) He should standby for notification by
should  assist  the  distant  technical  controller  in
maintenance of the distant technical controller that the
restoration of the baseband circuits, as required.
fault has been identified.
(4) If the faulty circuit has not already been
3-12. Examples of Voice Channel Fault
patched A out of service by stations at the distant
Isolation Procedures
terminals, and an extended outage is indicated, he
There are a number of acceptable methods of isolating
should assist in patching to a spare mux channel.
a faulty link in a communications channel.
(5) Upon notification that the equipment
methods are explained in this paragraph.  The first
malfunction has been corrected, he coordinates with
method (discussed in a and b below) requires the
stations involved to restore the circuit to the normal-
isolation procedure to begin at the point of fault
through configuration.
Each site clears his TCF of any
(6) He then completes station records, logs,
responsibility for the fault by working in order along the
and trouble reports.
communication chain. The second method (discussed
b. Noise Burst on a Local Subscriber Circuit. The
in c) allows the responsible TCF to isolate the fault over
technical controller is notified by a connected (local)
the whole communications chain by having his own
subscriber that frequent noise bursts are being received.
signal looped back and tested at various points in
The controller realizes that he is responsible for
succession along the chain.
coordinating fault isolation procedures at distant stations
a. Noise Burst on Mux Through Circuit. The local
which may be involved; however, he first determines if
technical controller is notified by a distant technical
the fault is in his own TCF.  He may decide to
controller that noise bursts are being encountered by
immediately patch to a spare channel by coordinating
one of his local subscribers. He had cleared his station
with the TCF which originates the signal, depending on
and wishes the local technical controller to do the same.
circuit priority and space availability. He should check
Since the circuit is relayed through this P&T, the local
the circuit in his P&T area by following a procedure
technical controller is responsible for simply checking
similar to that below:
the circuit through his site to determine if the fault
(1) The technical controller should attempt to
source is in his station, reporting back to the distant
clear his site and subscriber loop by patching a speaker
station, and correcting the fault, if necessary.  The
panel into the "REC MON" jack of the panel where the
technical controller could take the following action:
subscriber's circuit enters the P&T from the Mux system.
(1) At the Patch Bay electrically closer to the
If the noise is encountered, the fault is at some point
signal  source  and  away  from  the  complaining
closer to the signal source and away from the
subscriber, he should patch a speaker panel into the
subscriber. It is the local technical controller's duty to
monitor jack of the "LINE REC" appearance of the
coordinate further
circuit. If noise is encountered, the degradation must
originate at some point closer to the signal source,

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