Examples of Voice Channel Fault Isolation Procedures

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.

channel.

(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.

Two

(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.

recognition.

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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