In all kinds of switches, there is a displacement sensor that has a sense of proximity to its object. Using the displacement sensor to control the sensitive characteristics of the object to reach the control switch or the purpose of breaking, this is the proximity switch.
When an object moves towards a close switch and is close to a certain distance, the displacement sensor has a "perception" and the switch moves. This distance is usually called "check-out distance". Different proximity switches detect different distances.
Sometimes the object is detected at a certain time interval, one by one moving toward the proximity switch, one by one, and so on. Different proximity switches have different responsiveness to detecting objects. This response characteristic is called "response frequency".