Polarized telegraph relays

This paper is to discuss two forms of polarized telegraph relays which have been developed by the Bell System and applied originally to the metallic telegraph system. One of these relays was designed primarily for operation under severe and exacting circuit conditions and the other for application generally. Both relays are of the same general construction except that the former is more sensitive than the latter and is furnished with an auxiliary accelerating winding. Furthermore, this relay has incorporated in it certain refinements in construction and materials, which cause it to be extremely sensitive and to give reliable service for a comparatively long period without attention. The construction is of special interest in that the polarizing force of the permanent magnet is neutralized by the mechanical restraining force of the armature. A magnetic material having characteristics well suited to relay design and a new contact material are employed, which greatly improve the operating characteristics of the relay.