Post-war and on to 1975 (continued)

As the ELSA system was introduced and as STD grew, methods had to be devised to enable transmission equivalents to be regularly determined from a testing centre. The approach adopted involved a Self Answering Relay Set (SARS), not really a new concept, connected to a test number which could be accessed by dialling over the trunk line either using an automatic routine or, in the case of a small exchange, a manual tester. The testing equipment required included:

• an oscillator with a stable output level,


• a stable receiver which would operate a relay if the input exceeded a certain level,


• a standard test frequency.

Appropriate equipment was developed and in the early months of operation, for instance, in the Melbourne ELSA area, disclosed a high fault incidence. Many of these faults were quickly located and rectified but some intermittent problems proved more difficult. Further development of Automatic Trunk Transmission Testing equipment and practices followed. Salter48 for instance, describes a transmission level checker, developed by AWA in response to an APO schedule, for use by the telephone technician at a 2 wire exchange and used to access a call answering relay at a distant centre.Appropriate equipment was developed and in the early months of operation, for instance, in the Melbourne ELSA area, disclosed a high fault incidence. Many of these faults were quickly located and rectified but some intermittent problems proved more difficult. Further development of Automatic Trunk Transmission Testing equipment and practices followed. Salter[48] for instance, describes a transmission level checker, developed by AWA in response to an APO schedule, for use by the telephone technician at a 2 wire exchange and used to access a call answering relay at a distant centre.

In the earlier days of automatic telephone service, maintenance systems here and elsewhere were based on preventing faults occurring through a system of regular attention to the individual items of equipment. This was known as Preventive Maintenance. However, beginning in North America, this approach began to be queried with a shift towards a system which became known as Qualitative Maintenance, with emphasis on the measurement of overall grade of service and identification of those components adversely affecting performance. Thus these new methods, which began to be experimented with in Australia, required the production of indicators of the grade of service given by an exchange and by its components. Subscribers complaint analysis, service observations and automatic test calls were useful methods of providing exchange indicators, while other analysis was necessary to provide information on segments within the exchange. G. Moot, who was one of the pioneers of Qualitative Maintenance in the APO, has given an account of the philosophy behind the new approach and of the development of practices in the APO.[49]

Australian Academy of Technological Sciences and Engineering