An analysis of the problems of long-line telephone signalling

Automatic working of long lines means that all parts of a telephone network become interlocked, so that, for example, lack of an end-of-selection indication in a local exchange in Norway can create difficulties for a trunk-board designer in Spain, if ever (no matter over how many intervening tandem points) the two become interconnected. The present paper attempts to analyse the probable requirements and interactions arising from such automatic working, and deduces tentative principles for the co-ordination of design of trunk boards, trunk test-boards, long-line signalling equipment, and local automatic switching equipment. It is claimed that standardization of the principles laid down would minimize interaction difficulties and would leave the way open for future growth and for new developments.