Photoelectric switch say again photoelectric sensor , sensor points diffuse reflective type , feedback , duishe type , sensor and PLC and single-chip microcomputer , sr circuit ,electronic counters , solid state relay , small relays , etc products with magnetic use . The transmitter aims at the target and generates light beam , and ther receptor turns the light energy received into current and transmits it to the detection circuit backwards . It can filter our and effective signal and use it .