Telephone subscribers' monitoring equipment for electromechanical exchanges

Abstract

In the existing telephone network, modern digital technology, such as the CIT Alcatel E10 exchange, coexist with the older generation technology, such as the electromechanical Strowger and the German EMO equipment. One of the main problems associated with such a scheme is the non-uniformity of exchange facilities provided. Thus, if in digital exchanges, traffic measurement facilities, for instance are incorporated in the system, in the older systems this provision must be affected by a separate unit. Most of these facilities have a monitoring nature, i.e., collecting data from various points within the exchange and processing the data to give an interpretable output. Thus a ‘universal’ monitoring system by which some of the facilities offered by the newer exchanges could be duplicated would be most welcome in an electromechanical environment. Such monitoring functions would include for example, traffic measurement, subscriber monitoring and exchange circuit performance analysis. This project, while providing the hardware for a 'universal' monitoring unit, handles specifically the subscriber monitoring problem. What is and why is the need for telephone subscriber monitoring? Subscriber monitoring involves the recording of any subscriber set activity. The monitoring activity is usually requested by the subscriber himself; the subscriber may complain of excessive taxation and would like to prove to the authorities that his average call rate is less than that taxed. The subscriber could also want to monitor any unauthorized use of his telephone set. Exchange personnel could also wish to check for any faulty operation exchange apparatus for example, the metering process of a particular subscriber. The exchange staff could connect the subscriber in question to the monitoring equipment for a period of time, during which all or part of the subscriber activity is recorded and then analyse the observations. What would be the requirements of a subscriber monitoring unit? In the light of the existing telephone network characteristics, the unit must have certain properties to make it a versatile system, thus: 1. It must be a stand alone system, the only extra requirement being a standard commercial printer, and independent from any other system so that it can be set up in any, or most, of the electromechanical exchanges. 2. It must be compatible with different types of electromechanical exchanges, thus ensuring exchange type adaptability. 3. It must have reasonable capacity; statistically a 32 subscriber capacity would suffice for a 10 000 line exchange, since at any one time only a very small percentage of the exchange capacity would require observation. 4. The actual points to be monitored must be easily accessible (preferably on terminal blocks) so that minimal set up time is required. 5. The unit must be programmable, for example, a redundant subscriber connection can be made available to another subscriber, or different subscribers could require different types of data output. 6. The unit must produce a hard copy record of the calls’ details (for example, time of call initialisation, number dialled, time of answering, call termination time, etc.). This could be achieved by a printer connection, since the records would eventually be used in further administrative paperwork and 7. It must be reliable as a system and must be independent of any exchange faults. This project caters for the above specifications and the other technical requirements which will be discussed further in the text.