Recent developments in Bell System relays — Particularly sealed contact and miniature relays

Relays are among the most important electromechanical devices. They have been in use for many years and continue, in modern form, to be Essential elements in modern Bell System and military applications, including electronic switching systems. The most important recent developments are miniaturization, sealed contact relays using glass-enclosed contacts, and “remanent” type devices. Ferreed and bipolar ferreed coordinate arrays and individual units are new and important switching elements. These devices make use of miniature glass-enclosed contacts in combination with “square loop” magnetic material∗ such as ferrite or certain iron alloys. They are magnetic “latching” units and are operated or released by short pulses.