Relay

[1] An electro-magnetically operated switch used to make and break the flow of current in a circuit. As low amperage current is passed through one circuit of the relay, it switches and permits a greater current through another line. For example, when installing auxiliary lights with a heavy draw, the stock light switch may not be able to take the current. Thus a relay is installed so that when the light switch is turned on, low current is sent to the relay. The relay closes the circuit of heavy wiring directly from the battery to the lights. Also called "cutout" and "circuit breaker".
[2] An automatic device which controls the setting of a valve, switch, etc. by means of an electric motor, solenoid, or pneumatic mechanism. See cutout relay, hot-start pulse relay, time delay relay