A proximity fuze is a fuze that is designed to detonate an explosive

Explosive material

An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...

 device automatically when the distance to target becomes smaller than a predetermined value or when the target passes through a given plane. The proximity fuze should not be confused with the common contact fuse

Contact fuse

A contact fuze, percussion fuze or direct-action fuze is the fuze that is placed in the nose of a bomb or shell so that it will detonate on contact with a hard surface....

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One of the first practical proximity fuzes was codenamed the VT fuze, an acronym of “Variable Time fuze”, as deliberate camouflage for its operating principle.