Choice of a telephone switching system

An often neglected approach to choosing the right telephone switching system is to consider the views of the three parties involved rather than the circuit and component characteristics of systems. The three parties are the telephone user, the operating administration and the manufacturer, together deciding on the required features and the economic cost of the systems. The telephone user is expecting better and more facilities of which a number are given as example. The administration has to consider the subscriber's views, but also the optimum use of capital, its division between the network's constituent parts as exchanges, local and trunk networks, and the service reliability. To the manufacturer the design lifetime will decide whether cost can be minimized and system reliability and features can be improved. The remainder of the article deals with comparing direct and indirect switching systems, open and closed numbering schemes, apparatus and signalling.