A solid state relay (SSR) is an electronic component that switches power to a load circuit and provides electrical isolation between an application’s control circuit and load circuit. It is a competitive technology to electromechanical relays, contactors and other switching technologies such as mercury displacements relays. Basically solid state relays are components that control power to a load just as electromechanical relays do, except without some of the limitations. In a typical wiring of an SSR, in a load circuit, note that the load may be placed in either power leg connected to terminal 1 or terminal 2 of the SSR. For DC relays, correct polarity of the power supply, load and relay must be observed.