Disconnect switches, also called safety switches or simply disconnects, are used to ensure an electrical circuit is completely cut off from its power source for service or maintenance.
They are not usually intended for normal control of the circuit, and thus typically open or close only after current has been interrupted by another device. Some applications use disconnects as fault protection for heavy machinery. Disconnect switches also often have lockout-tagout provisions, to prevent inadvertent or unauthorized operation.
As a primary safety disconnect device, disconnect switches are an NEC requirement in industrial and manufacturing facilities established by the National Fire Protection Association (NFPA).