A relay is an electromechanical switch that uses an electrical signal to connect or disconnect two circuits. It serves to protect electrical systems and connected equipment from over currents or voltage and can open and close circuits electromechanically or electronically. Relays can control high voltage circuits with low voltage signals in applications such as audio amplifiers and modems and are found in control circuits in larger systems, sometimes also used in protective environments to prevent equipment damage by detection of abnormalities in a circuit. They can also control high current circuits with low current signals, as seen in automotive starter solenoids. Relays are widely used in lighting control systems, telecommunication, industrial processes, traffic control, motor drives, power system protection, computer interfaces, automotive systems, and home appliances.