Catastrophic Failure

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

DCA or ACC.

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.

Circuit

4-15.

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

Section III. PATCHING OPERATIONS

4-17. Pu

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

terminal.

ing.

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

4-5