Found in factories, power plants, and process facilities, they house components such as PLCs, relays, HMIs, and circuit breakers that keep equipment running efficiently. An electrical switch is any device used to interrupt the flow of electrons in a circuit. Switches are essentially binary devices: they are either completely on (“closed”) or completely off (“open”). In industrial. The general types of commercial control systems include the following: Programmable logic controllers (PLCs): PLCs are discreet, versatile controllers for specific functions on robots, production lines, or conveyors.