The design of a polarized telegraph relay

Polarized telegraph relays have been used since the early days of the telegraph, but information regarding the design has hitherto been limited practically to a discussion of static conditions only. The paper discusses static and dynamic conditions of polarized telegraph relays. From the point ofview of performance relays are divided in two classes, viz. those with stiff and those with springy tongues. It is shown that a satisfactory performance as regards short transit time and freedom from chatter can only be obtained with relays of the second class. The necessity for damping the motion is pointed out. In the latter part of the paper a practical design based on the theoretical part of the paper is described, and various test methods are discussed with regard to this design.