You searched for: “proximity sensor”
proximity sensor (s) (noun), proximity sensors (pl)
A device that detects the presence of an object and sends a signal to another device: Proximity sensors are often used on manufacturing lines to alert robots, or are routing devices on a conveyor belt to forewarn the presence of an object that is approaching.

This entry is located in the following units: Radio Frequency Identification (RFID): Definitions (page 8) senso-, sens-, sensi-, sensori-, sent- (page 5)