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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
isolated to that particular area. In such a case, proceed
m. Test the common circuitry of the multiplex ter-
as follows:
(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.
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.
(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
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
(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.

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