Relay switches use a small amount of power to control a larger source of power connected to electrical devices such as car motors, computers, and lighting installations. A basic relay switch has a control circuit with an electromagnetic coil and a load circuit with contacts and a lever. When current flows into the relay switch, it moves through the coil and a magnetic field is created, which causes the lever in the load circuit to move between contacts, either turning the device on or off. In a normally open (NO) relay switch, when power is supplied to the relay, the load circuit is closed and the power source connected to the relay is turned on. In a normally closed (NC) relay switch, when power is supplied to the relay, the load circuit is open and the power source connected to the relay is turned off. In other types of relay switches, non-moving parts such as transistors or semiconductors can be used as the control circuit to operate the switching mechanism. Relay switches can be controlled with an external switch, such as a light switch, or they can be connected to an automatically switched power source, such as a car ignition. One relay can operate multiple switches, and multiple relays can be operated with a single switch, with each relay operating independently from the other relays in the system.