Any device used to interrupt the passage of electrons in a circuit is called an electrical switch. Switches are basically binary devices: they are either fully open ("closed") or fully closed ("open").
Switches are manufactured in multiple configurations; they may have multiple sets of contacts operated by the same knob or actuator, and the contacts can work simultaneously, sequentially, or alternately. The switch can be activated manually, such as a light switch or keyboard button, or it can be used as a sensor device, such as a thermostat, to sense the position, liquid level, pressure, or temperature of machine parts.
There are many specialized types of switches, including toggle switches, rotary switches, mercury switches, push button switches, reversing switches, relays, and circuit breakers.
There are many styles of switches.
The switch can be directly operated by a person as a control signal for the system, such as a computer keyboard button, or it can be used to control the power flow in a circuit, such as a light switch. A relay is a switch controlled by another circuit.
The motor drive mechanism can be used to remotely operate large switches. Some switches are used to disconnect power from the system, provide a visible separation point, and if necessary, can be padlocked to prevent accidental operation of the machine during maintenance or to prevent electric shock.