The proximity sensor is a sensor device that determines how close another object is.
It was a proximity alarm had warned Cadet Jean Hajar of an impending collision with Cadet Joshua Albert's training craft, allowing herself and her Nova Squadron teammates flying in tight formation to initiate their emergency transporters before their ships were destroyed in the ensuing pileup.
Lieutenant Jadzia Dax had to repair the proximity systems on an abandoned, decrepit Bajoran raider hidden under lest Dax and Major Kira Nerys started "bouncing off the walls". (DS9:"The Siege")
Military uses
Proximity sensors are commonly used on mines, where it triggers the mine's detonation when it nears or impacts a target. A malfunction in the proximity sensors could cause the mine either to detonate prematurely or to not detonate at all. (DS9: "Call to Arms", ENT: "Minefield")
See also: proximity detector