Relays are a type of electrically operated switch, and they provide input terminals and operating contact terminals for their functionality. Depending on the relay, they may be implemented within a device in order to control a circuit with a low-power signal or several circuits with a single signal. In their infancy, relays served as signal repeaters for long-distance telegraph circuits as well as telephone exchanges. As more advancements were made to such electrical switch components, their applications widened to include a number of electronic systems and appliances for motor control, circuit protection, safety-critical logic procedures, and more. While a number of relays exist to facilitate numerous needs, the three primary types that are most often used include the electromechanical, solid-state, and reed relay.