Photoelectric switch (photoelectric sensor) is the abbreviation of photoelectric proximity switch, it is the use of the detected object on the light beam blocking or reflection, by synchronizing the circuit to turn on the circuit, so as to detect the presence or absence of the object. Objects are not limited to metal, all objects that can reflect light (or have a blocking effect on light) can be detected. The photoelectric switch converts the input current at the transmitter into a light signal that is emitted, and the receiver then detects the target object based on the strength or presence of the received light.