Interlock

Interlock is a mechanism or system that prevents progression or access until preconditions are met, or that enforces safe sequencing between components. It is used in mechanical engineering, electrical control, process safety, and transportation. Interlocks may be physical devices, such as locks and switches, or logical constructs in control software.

In machinery, an interlock typically blocks the start of equipment when a guard, door, or access point is open. This is a common form of safety interlock; the device may be a mechanical latch that must be engaged or an electric switch that stops power when opened. Electrical interlocks coordinate multiple actions; for example, a two-hand control or a door interlock to ensure that safe conditions are established before a cycle begins. In railway systems, interlocking prevents conflicting movements by locking signals and track switches in safe positions.

In textiles, interlock refers to a type of double-knit fabric produced by interlocking loops on both sides, yielding a stable, smooth surface. The term can also be used as a verb, meaning to lock or connect parts together. Interlock systems are often subject to standards and best practices for safety, including proper installation and periodic testing.