Development of Reed Switches and Relays

Improvements in the operating speed, efficiency, compactness and contact reliability of relays may be obtained from the application of sealed-in-glass reed switches. This paper is an account of the development of such switches and relay designs suitable for their use. Because of the close dependence of contact performance and switch operating characteristics upon process methods their development has been an important part of this project. I -- REED SWITCHES Switches are those basic circuit elements of a telephone system which make it feasible to establish the connections desired by telephone users. To permit remote operation, switches in the telephone plant are usually electromechanical devices and they are used to select and establish needed talking paths. Since switches are used in large numbers their manufacturing and operating costs have a significant impact upon telephone economics and for this reason the development of switching apparatus receives much attention. HISTORICAL In 1936 the availability of new magnetic alloys prompted a study of improved means for the operation of switching contacts. As a part of this work there was conceived an extremely simple magnetic structure giving promise of excellent electromechanical efficiency, unusually high operating speeds and lending itself to very compact designs. This paper is an account of the development of this basic concept to the point of practical application in the Bell System. The basic concept is shown in Fig. 1. Two flat reeds of magnetic material are supported as cantilevers with their free ends overlapping and separated by a small gap.