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TM 11-5895-1012-10
prior to getting the circuits back into service. Any non-
patching type rerouting actions required to restore
ACC and/or higher headquarters.
service to less than highest priority critical circuits
must be first coordinated with or have the approval of
4-16. Catastrophic Failure
The failure of link equipment, transmitters, or multi-
channel equipment involving critical highest priority
pleted, and the circuit verified in service, the station
circuits, either by error or intent of man, or by natural
records are updated and details promptly forwarded to
forces, are considered catastrophic failures. Under
ACC in order that the system master files and records
these conditions, the restoration of service to critical
can be maintains current at all times.
and high priority circuits is of paramount importance.
Of equal importance at this time is the need to notify
ACC of the failure event, the point of failure, extent of
Any circuit rerouting necessitated by system, equip
damage, estimate of work, equipment, and time in-
ment, or facilities failure can be identified as an emer-
volved in correcting the failure, and what has been
gency requirement. Emergency circuit rerouting is ac-
done or is being done to restore service. Station super-
complished in so far as possible, by temporary cord,
visors and station Technical Controllers immediately
plug and jack patching arrangement? at or through the
take action to reroute predetermined critical and high
Technical Control Facility using installed spare equip
priority circuits to the maximum degree possible over
ments or channels to bypass the failed equipment or
available spares whenever alternate routing links are
portion of the circuit or system. The magnitude of fail-
available. As services are restored, DCA and ACC are
ure will determine the degree of emergency attached
notified. DCA or ACC evaluates initial reports and all
to each service interruption. A majority of the service
subsequent status reports and initiates necessary in-
troubles encountered can be attributed to failure of a
structions to Station Supervisors and Technical Con-
minor item of in-station equipment; in this case, the
trollers detailing additional circuits to be rerouted and
station personnel are able to restore service expedi-
routes to be used. DCA or ACC also indicates which, if
tiously by patching in spare equipment or components.
any, lesser priority circuits will be preempted in order
As soon as maintenance personnel repair or replace the
to maintain a maximum service balance throughout
failed items, the circuit is restored to its normal path.
the entire system until the failures can be completely
All troubles must be logged and reported, but the use
restored to normal service.
of installed spares need not be coordinated with ACC
of Patching
and/or channels usually locates the trouble. Often, it is
possible to patch out all station equipment in one
Patching is defined as the rearrangement of the elec-
patching operation, establishing quickly whether the
trical interconnections among items of station equip
fault is in any of the local station's equipment. Once a
ment by means of pat&cords and jackfields.
channel or equipment has been patched out, test equip
a. Service Restoration. The various patching facili-
ment is employed to evaluate circuit performance and
ties provided in the station Technical Control area en-
to localize the trouble.
able the Technical Controller to take positive action to
c. Service Continuity During Maintenance. Pre-
restore service when a circuit failure has been localized
ventive maintenance routines require periodic quality
to a station. Such restoration action consists of bypass-
control tests (Section VI) and adjustments of channels
ing the defective equipment and substituting like
and station equipment. When it is necessary to con-
equipment from the complement of operational spares
duct such tests on assigned channels or equipment,,
and, similarly, substituting spare, or lower priority,
service is maintained by a patching substitution. Fault
channels for those degraded or inoperative. The substi-
isolation (Section IV) requires that the defective equip
tution of equipment usually involves only a local
ment is disconnected from the circuit and a spare sub
patching operation, while substitution of channels re-
stituted. This substitution is accomplished by patch-
quires a coordinated patching operation at the distant
d. Operational Spares. Operational spares facilities
b. Fault Isolation by Substitution. Substitution of
station equipment and channels by patching opera-
consist of spare multiplex and VFCT channels and
a valuable fault isolation technique. A logical
selected items of equipment cross-connected into
specific spare configurations. Whenever such spare
re of successive substitutions of equipment

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