Fuze

A fuze is an electronic, pyrotechnic or mechanical system that initiates the detonation of a warhead, bomb, or other piece of ordnance. It may be as simple as a device that senses contact with the target, or as complex as a computing system that counts the number of airspaces penetrated by a bomb entering a building and triggering the detonator on a specific floor.

A fuse is a specifically pyrotechnic device that conducts a flame to a heat-sensitive detonator.

Basic fuzes trigger on some mechanical event, such as impact, the application of pressure (e.g., weight on a land mine, the release of pressure (e.g., the breaking of a trip wire) or the tilting of a rod. More complex fuzes are based on one or more timers, as, for example, one that initiates some number of seconds after a projectile is fired from a gun, and causes the warhead to burst in the air.

Proximity fuzes were the first electronic fuzes, which trigger when they come within a certain distance of a reflector of radio waves, such as a moving aircraft, or a certain height over ground. Magnetic influence fuzes, most often used against ships but also against targets such as tanks, trigger due to the change in magnetic field induced by a large mass of ferrous metal.

The availability of computers allow such selective fuze actions as detonating on hearing a specific ship propeller sound. Computer control can also delay detonation to wait for some number of events, so the fuze might ignore sacrificial low-value targets and actuate only for the protected target.