A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple … 展开

Electrical relays got their start in application to telegraphs. American scientist Joseph Henry is often cited to have invented a relay in 1835 in order to improve his version of the electrical telegraph, developed earlier in 1831. … 展开

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core (a solenoid), an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of con… 展开