A triggering device attached to the machine gun armament of fighter aircraft so that the gun could fire through the arc of a spinning propeller without the bullets striking the blades.

Device preventing electrical shock hazards.

(electrical engineering) A type of circuit breaker that detects signs of potentially-dangerous arcing on downstream wiring and shuts off power to the affected branch circuit to reduce the risk of a fire.

In electrical engineering, a vacuum interrupter is a switch which uses electrical contacts in a vacuum.