IEE Electronics Division: Chairman´s address. Switching in space and time

Whereas for many years electronic techniques have had wide application in telecommunication transmission equipment, until relatively recently telecommunication switching equipment has been dominated by electromechanical techniques. However, this dominance is now rapidly disappearing as electronic techniques are increasingly employed in switching, often coupled with stored program (computer) control. As electromechanical techniques were introduced well over 50 years ago, it might be assumed that progress in switching has been relatively slow until the comparatively recent technological change. With particular reference to telephone switching systems, the paper aims to show this is not the case, and that considerable changes occurred even within the constraints of an electromechanical realisation. It is argued that, although the original move from manual to automatic control was necessary for economic reasons, it was not beneficial in all respects to the subscribers, and subsequent advances were often aimed at re-introducing facilities available with adequately staffed manual systems. The paper briefly outlines the fundamental principles of switching, which are first illustrated by reference to a typical manual realisation. The evolution of automatic systems is traced from the original step-by-step dispersed-control approach, through the introduction of electromechanical common control, to the introduction of electronics and stored program control. With the introduction of electronic, stored program controlled, digitally switched systems, it is suggested that we may be about to regain the flexibility of a manual approach, with the advantage that the systems should be better able to cope with the modern network environment, more economical to operate and more reliable in service.