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CCM - A Well- tried and Economic Maintenance System Verner Eriksson An article has been written and is published elsewhere in this number to mark the fact that it is now two years since CCM (Controlled Corrective Maintenance) was first introduced in the Rotterdam telephone district. Thanks to the valuable contributions of the Dutch and other telephone administrations in the field of maintenance of telephone exchanges it has been possible to further develop CCM to its present high level. The introduction of CCM has led to an improvement in the service quality of telephone exchanges, at the same time that the maintenance work has been reduced considerably. In the following article the author summarizes the CCM method. while carrying out their repair work the exchange staff unintentionally caused more faults, the number of which increased with the size of the staff. However, this expensive and inefficient method of preventive maintenance was gradually changed, to a great extent due to the rapid development of new and more reliable telephone exchange systems with facilities for efficient and automatic supervision. UDC 621.395 722: 658.581 LME 154 Fig. 1 Operation control room for the Mollison international transit exchange in London Up to 25 years ago comprehensive preventive maintenance work was carried out as a general rule in telephone exchanges, in an attempt to achieve good service quality. This preventive maintenance had many disadvantages. For example, it was possible to show that When the first ARF exchange was installed in Helsinki in 1950, the time was ripe for studying the maintenance question in detail, with a view to replacing the increasingly expensive exchange staff by automatic supervisory equipment. In order to increase the scope and depth of these studies, in 1956 LM Ericsson invited the Nordic
135 VERNER ERIKSSON Telephone Exchange Division Telefonaktiebolaget LM Ericsson telecommunications administrations to the first maintenance conference in Stockholm. During a corresponding conference in 1957, the Swedish Telecommunications Administration reported that they achieved a better quality of service, with reduced maintenance, in their AGF type of 500-line selector exchanges since they introduced the basic CCM principles. When should maintenance measures be taken As has been said earlier, it has been shown that it is uneconomic to repair all faults as soon as they occur, and maintenance measures should not be resorted to until the service quality tends to fall below the level that the subscribers have a right to expect. How is it then possible to determine when maintenance action should be taken The economic situation of a telecommunications administration is made clear by the book-keeping. The technical management of the administration has every reason to keep corresponding »books» for different forms of service statistics. From these it is possible to determine the quality of the service that the subscribers receive, which in the long run gives the fault trend. Moreover, in order to supervise the function of telephone exchanges continuously, it is necessary to introduce supervisory equipment that works on a statistical basis. Modern exchanges contain such equipment, which in the main supervises only the function of the exchange itself. Consequently, it is often necessary to supplement this with autonomous equipment, primarily an automatic traffic route tester, TRT. This is an invaluable aid, which makes possible an efficient CCM. The traffic route tester has been described in an earlier issue of Ericsson Review 1 . Important principles In order to achieve the best possible result the following main principles should be observed. IZ Do not interfere with the equipment more than is absolutely necessary. Fig. 2 a Example of how a modern electronic traffic route tester can be used in a network TRTM Central and controlling unit, which Initiates all test connections. It also registers the correctness, transmission level and tariff Impulse functions etc. for each test connection TRTS Combined terminating and traffic generating unit, controlled by TRTM CA Terminating unit OMC "Operation and maintenance centre Group switching centre ® Subordinate exchange 9 Terminal exchange
Page 1: ERICSSON REVIEW 3 1976 GEOSTATIONAR
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