Dc Fault Isolation

TM 11-5895-1012-10

(2) Request the distant Technical Control Facility

o r e q u i p m e n t to more than one receiver.

to send a teat signal on the faulty channel.

l. Direct maintenance personnel to perform receiver

(3) If the results of the test procedure are unsatis-

common base-band equipment tests to verify nor-

factory at a certain point, the trouble will have been

operation.

isolated to that particular area. In such a case, proceed

m. Test the common circuitry of the multiplex ter-

as follows:

minal.

(a) In coordination with the distant technical

n. When the malfunction has been isolated and cor-

control, determine which equipment is at fault (for ex-

notify the distant Technical Controller of the

ample, VFCT keyer or converter, line conditioning

of the problem and request removal of the test

equipment, etc.).

signal. If necessary perform additional out-of-service

(b) Coordinate the equipment repair or align-

testing to ensure that all circuits meet specified

ment required tocorrect the fault.

(c) If equipment is found to be unuseable, coor-

o. Restore user service to normal when the correc-

dinate with station maintenance personnel for its re-

tive action has cleared the malfunction.

placement.

p. Complete station reports, trouble reports, log en-

(d) After repair or replacement, perform the ap-

tries etc., in accordance with the established proce-

propriate test to ensure proper operation of the circuit.

dures.

(e) Notify the user that the fault has been

4-33. Dc Fault Isolation

cleared, and restore service to the normal route. Serv-

ice shall always be returned to the normally assigned

When the Technical Controller discovers that one or

channel at the earliest possible time.

more dc circuits are not operating properly, in-service

(4) When the test signal from the distant TCF is

monitoring tests should be performed in accordance

satisfactory, request a test signal from the distant sub

with established station procedures to determine if a

scriber to determine whether the fault is between the

single channel or the entire VFCT group is faulty. If

distant subscriber and distant Technical Control Facil-

the entire VFCT group is affected, the Technical Con-

ity or between the local TCF and its subscribers. The

troller must continue monitoring to determine

Technical Controller at both ends of the circuit should

whether the fault is within the voice frequency sub

monitor the subscriber's test signal, and in that way

system, the multiplex channel equipment, or the local

or distant VFCT equipment. If the fault is not in the

isolate the fault area.

VFCT equipment, the controller should refer to para-

(a) Coordinate the repair or alignment required

graphs 4-28 through 4-32 and apply the applicable

to provide service between the DCS Station and the

procedures. Multichannel faults not involving the

local subscriber.

voice frequency subsystem or multiplex channel equip

(b) Perform the appropriate tests to ensure

ment are limited to send or receive VFCT equipment.

proper operation of the circuit over the lines between

the DCS Station and the local subscribers.

The Technical Controller should proceed immediately

to effect isolation of the fault within the portions of

(c) Notify the user that the fault has been

the VFCT which are common to all channels. Single dc

cleared, and restore service to the normal route.

channel faults may be located by coordinating with the

(5) Complete station records, trouble reports, log

distant station to selectively eliminate each portion of

entries, etc., in accordance with the established proce-

the circuit which is performing properly. In-station

dures.

monitoring procedures may often locate the fault to a

b. When it is determined that all channels within a

general area which will permit a modification of the

multichannel VFCT system are unuseable, the Techni-

fault isolation procedures and attack the problem

cal Controller shall proceed as follows:

directly, either by substitution of equipment by patch-

(1) Notify the distant Technical Control Facility

ing or replacement of equipment. Out-of-service test-

to block user input on all channels. Notify users that

ing procedures or in-station test and alignment proce-

the circuit has failed, and deactivate all traffic equip-

dures can then be applied to locate and correct the

ment.

fault.

(2) The cause of failure could be in the voice fre-

a. When it is determined that one channel of a

quency channel or in the VFCT equipment. Perform

multichannel VFCT system is unuseable, the Techni-

the voice frequency fault isolation procedures as de-

cal Controller should proceed as follows:

scribed in paragraph 4-30.

(1) Coordinate with the distant Technical Control

(3) If the results of (2) above are satisfactory, re-

Facility to restore service on a spare channel or pre-

quest the distant TFC sent a test signal on specific

empt a low priority user. If a low priority user is pre-

channels. Channels 1, 8, and 16 of the VFCT equip

empted, have the distant Technical Controller notify

ment are preferred test tone channels. Proceed as fol-

the user of preemption of the circuit.

lows:

4-19