Skills of the kind required are in great demand and frequently in short supply, and there is no doubt that the demands for such skills can be eased by the use of Automatic Test Systems which, however, because of their investment cost, are only economic if they handle very large numbers of units.
During the past two years the Directorate has examined Automatic Test Systems (ATS), and has considered how they might best be employed. The factors to be taken into account are as follows:
a. Economic use of ATS demands full employment of expensive equipment which in turn implies centralised repair of large numbers of units.
b. The present system, built up over a number of years, whereby skilled technicians are outstationed close to centres of customer activity, performs a very useful function in many ways, and it would be a pity if centralised servicing led to their disbandment.
c. Mobile and main station equipments are too bulky for easy transportation in large numbers.
Bulk transportation of Firemen's alert receivers in special transit cases is no problem, in fact units from the North of England can be at Bishops Cleeve (our central repair depot) in five hours.
This receiver has been chosen for the first excursion into automatic testing and Messrs Marconi Instruments have been entrusted with the task of producing a system, which should be coming into service at the beginning of 1972.
Although automatic testing has been highly successful for a number of years, particularly in the aircraft industry, the step which we now propose to take will involve reliable interconnection at radio frequencies without the use of special connectors. Nowhere in the world has this been done before, and the Directorate is therefore breaking new ground, as it did previously with Police Pocketfones and batteries.
The system by which the Service will be supplied with serviceable alert receivers is a very simple one. Outstations and depots will retain serviceable spare equipment which will be uncoded and therefore suitable for use at any station . When an unserviceable unit is received, it will be given a simple go/no go test to ensure that the coding unit is serviceable. The coding unit will be removed and inserted into the serviceable receiver which will be tested and handed over on a one for one basis.
The application of automation to mobile equipment maintenance need not be incompatible with the retention of outstations, or with Service Communications Personnel playing a full part in maintenance of their communications. A three stage system would operate as follows:-
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:-
continued on page 2 ....Acknowledgement: Home Office DOT Exhibition 1971 Papers