Discussion on, “time-limit relays”, and “duplication of electrical apparatus to secure reliability of service”, at New York, May 16, 1905

H. G. Stott: The ordinary overload relay as described in Mr. Chellis´ paper is employed to do the opposite of what the telegraph relay does : that is to say, the telegraph relay is used to apply a strong current to operate the receiving apparatus, while the purpose of the overload relay is to apply a comparatively weak current to operate a switch apparatus, because the main current has reached such pressures and strengths that it has become exceedingly expensive if not impossible, to design relays to work on main-line current. Different requirements have called for the design of different types of relays. The principal types mentioned in the paper — the overload, the differential, and the reversed-current, all have an application which is very concisely described in the paper.