a set of methods and facilities that ensure holding the operating parts (components) of an apparatus, machine, or circuit (electrical) in a definite state which is maintained regardless of whether the interlocking action ceases. Interlocking increases the safety of service and the operating reliability of equipment, ensures the required operational sequence for mechanisms and components, and restricts the motions of mechanisms to the limits of the operating zone. The state (position) of operating parts in an object is held, depending on the operating principle of the interlocking device, by mechanical, magnetic, optical, or electrical means. Interlocking is discontinued by an action that returns the locked portions of an apparatus, machine, or circuit to the initial condition (before the interlocking) or permits a transition into another operating position by the presence of a corresponding signal. Interlocking can be achieved by manual, semiautomatic, and automatic means. In electrical equipment or in equipment having an electrical control, an interlock is set up to counter simultaneous actions or an incorrect sequence of connections or disconnections by interrupting the electrical power circuits; in machines with a hydraulic drive, an interlock shuts off the valves in the supply system; and so on. For example, in domestic gas hot water heaters there is an interlocking device that turns off the gas supply if the inflow of water is interrupted.
Interlocking is extensively employed in transportation, electric power stations and substations, industrial plants, computing equipment, and various production and domestic apparatus and devices.
I. E. DEKABRUN