DIRECTORATE OF TELECOMMUNICATIONS
THE FIELD ORGANISATION
By: A N Holdstock
page 4 of 8


a. First Line Servicing

Simple assessment of the location of the fault within the vehicle installation by Service Communications Personnel, and fault rectification by replacement of main equipment, controller, or speaker, from equipment either held as rented spares or removed from a less essential vehicle.

b. Second Line Servicing

Repair of controller, replacement of speaker, or breakdown of main equipment into sub-units followed by replacement of such sub-units found to be faulty. This work would be carried out by outstation personnel.

c. Third Line Servicing

Fault diagnosis of sub-units down to component level, followed by replacement of faulty part. This work would be carried out at a central depot using Automatic Test Systems as appropriate. Transportation of faulty equipment would follow the existing pattern for pocket equipment. Units would be replaced on a one for one basis.

Gradual fall-off in the performance of mobile equipment has always presented a problem. The system of daily tests of an equipment at its home location will prove that the equipment is working, but unless the home location is in a poor reception area it will not prove how well it is working, or ensure that when the vehicle is at an incident , in a poor reception area, the all-important message can be passed.

Preventive maintenance - recently restarted - can be the means of locating many faults which contribute to poor communications.

Main Station Eguipment

Two systems are used at present for diagnosing faults at main stations:

a. The Regional Depot can monitor the main transmitters of a scheme on a panoramic adaptor which displays the outputs of the transmitters side by side on a cathode ray tube. From this display the technician at the depot is able to say which transmitter is faulty.

b. The Service operator can make a series of tests with mobile units and from the results of these tests make an assessment as to the probable location of the fault. "Probable" is used because correct diagnosis depends on many factors, quite apart from the need for a highly skilled operator.

As a result of these diagnostic processes, either a technician will proceed to the location of the fault, the Service operator will make a bay change and test again, in accordance with a standard plan.

This approach suffers from the disadvantage that in the case of depot tests insufficient information is available to make a complete diagnosis, and in the case of the Service operator tests the information is not sufficiently positive to ensure correct diagnosis. Using existing operational equipment, a special switching system and an additional special receiver capable of resolving main transmitter outputs individually, it is possible to diagnose a fault to a particular unit at a particular site without tests with mobile units. The advantages of such a system, coupled with the ability remotely to change individual units instead of bays, are as follows:-

Source: Home Office DOT Exhibition 1971 Papers

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