Proximity switches are about detecting movement.
Movements, which can be of a complex nature, and which occur for instance in machine components of automated production processes. Keeping track of them is necessary in order for the machines to function smoothly, both independently and in relation to each other. Huge amounts of information concerning movement and position need to be passed to and from the main control unit. And this in working environments that frequently mean dirt, oil, vibrations, and high temperatures. Proximity switches are also about quality control.