General Relay Terms. Relay. A device designed to cause a sudden, predicted change in a single or multiple electrical output circuits when certain conditions are satisfied by the electrical input circuit that controls the relay device.

What are the three types of relays?

The three main types of relays are electromechanical, solid-state, and reed.

How do you test a general purpose relay?

Grab a multimeter and set it to Ohms. Touch the leads across the electromagnet coil pins and measure resistance. Anywhere from 50-120 ohms is OK. Out of range or open means a bad electromagnet coil winding and time for a new relay.