Fault Isolation Procedures

TM 11-5895-878-14&P

equipment should be used to restore disrupted service

channel or group is not operating satisfactorily, the

while the defective equipment is being restored.

station technical controller proceeds in the following

manner:

(3) During prolonged, or projected extended

out-ages, the technical controller should request

(1) He determines if a single channel, a group

alternate routing instructions. Rerouting and preempting

of channels, or the entire area is affected.

is obtained from a list in SOP.

(2) The controller isolates the area of

(4) As a last resort, the technical controller

malfunction.

should preempt lower priority circuits in order to restore

(3) He then endeavors to restore service as

service for high priority users. Every circuit, including

quickly as possible by selecting the most expeditious of

switchboard trunks as well as allocated circuits, is

the following methods: By substituting in-station spare

assigned a priority of restoration which must be adhered

equipment of identical configuration by patching to a

to in channel restoration.

Establishment of these

spare channel between stations (figs. 3-1 through 3-3)

priorities is performed on a worldwide basis by the

and/or by requesting that station maintenance personnel

Defense Communications Agency.

perform the necessary testing and equipment repairs.

c. Records and Reports. The technical controller

(4) In the event that the malfunction involves

who first determines that a fault exists or to whom a

a priority channel, and service cannot be restored

fault is reported by a user, is responsible for

expeditiously by the above methods, he preempts a

coordinating the fault isolation activities with distant

channel from the lowest priority user by patching.

station controllers, and he is responsible for appropriate

b. Single Channel. When it is determined that a

log entries and reports. When a fault has been isolated,

single voice channel is unserviceable, the station

an explanation of the nature of the trouble must be

technical controller takes the following action:

entered in the reporting station log, and the distant

(1) If the fault notification has been received

technical controller must be notified so that the entries

from a connected subscriber, the controller should check

for both stations coincide. All circuit outages must be

the local subscriber loop to determine the serviceability

recorded on the appropriate station logs, regardless of

of the subscriber terminal equipment and of the

the duration of the outages time or the cause of the

transmission facilities between the subscriber and the

fault. Specific instructions for reporting of stations are

station. If it is found to be unserviceable, he should

contained in Standard Operating Procedures. Trouble

notify station maintenance personnel.

reports (work orders) must be prepared for each

(2) If the subscriber loop is determined to be

equipment or circuit failure. This work order will notify

functional, he should check the serviceability of the in-

maintenance of the faulty or substandard equipment.

station circuit path, including a check made in

Only by-strict adherence to this procedure can proper

conjunction with microwave personnel, of the multiplex

records be maintained. Prompt, efficient repair of faulty

channel modem assigned to the circuit.

If any

equipment often depends upon the completeness and

component is found to be unserviceable, he should

accuracy of the symptoms described on the written work

change cable pairs or request microwave personnel to

order.

restore service.

d. Catastrophic Failure. Normally, the technical

(3) If the in-station circuit path is determined

controllers keep the CCOC and DCA informed of

to be serviceable, the controller should request that the

anticipated or existing service failures or degraded

technical controller, at the next station where the circuit

conditions which are beyond the local capability to

appears, check the serviceability of the subscriber

restore within a tolerable delay or outage time period. In

circuit within its station. The fault isolation mission

an exceptional case, a catastrophic failure condition

should be continued, as necessary by coordination with

may be encountered in which the alarm indicator display

other technical controllers until the fault has been

may depict a number of simultaneous alarms or provide

isolated and corrected.

an indication of a second major alarm condition within

the same station before the first alarm has been cleared.

(4) If the malfunction occurred at a distant

In these cases, the SOC may provide alternate routing

station or between station, he directs and assists the

instructions, or other solutions, as applicable.

distant technical controller in the restoration of the

circuit, as requested.

c. Multichannel. When it is determined that an

3-11. Fault Isolation Procedures

entire group of 12 channels or supergroup of 60

a. General. The technical controller must keep in

channels is unserviceable, the station technical

mind that the fault isolation procedures which follow

controller should take the following action:

serve only as a guide for efficient technical control

operations and do not represent a rigid sequence of

(1) In conjunction with the station microwave

steps which must be followed to solve a problem. The

personnel, he should check the serviceability of the

site SOP should be adhered to if not in agreement with

station multiplex terminal equipment associated with the

the following. The technical controller is urged to

affected circuits. If any component is found to be

bypass any unnecessary steps in order to achieve the

defective, he should restore service in accordance with

most expeditious fault location and service restoration.

the service restoration guidelines (SOP). In the event

When an equipment alarm is activated, a fault notice is

that a spare group or supergroup is not available to

received from a user, or routine checks indicate that a

correct the deficiency

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