Relays

Abstract

A relay is defined as an electrically controlled device that opens and closes electrical contacts, or activates and deactivates operation of other devices in the same or another electrical circuit. Two types of relay technology are available, mechanical and solid state. A mechanical relay is essentially a combination of an inductor and a switch, where the electromagnetic force of the inductor causes a switch to change position. A solid state relay accomplishes the same function with semiconductor devices changing impedance to effectively activate or deactivate a circuit open or closed. This document is intended to be a general guide to aid the designer in the appropriate selection of a relay for the intended application. Detailed information on the selection and use of relays can be found in MIL-STD-1346.