A proximity fuze ( also called a VT fuze , for `` variable time '' ) is a fuze that is made to create an explosive when the distance to the target becomes smaller than a set value or when the target passes through a given line . A proximity fuze is a fuze that is designed to detonate an explosive 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 .