Principle of operation [t-head1-first]

The optoelectronic sensors in the switch operate using modulated infrared light. Visible light therefore cannot affect their operation. Infrared light can penetrate even severe dirt on the optics, and thus ensures reliable operation. Proximity switch transmitters and receivers are matched to one another. The sensor receiver has an integral bandpass filter to amplify primarily the transmitted frequency. All other frequencies are attenuated. This gives the units good resistance to extraneous light. Precision plastic optics ensure long range and long sensing distances. There are two types of optical proximity switch, distinguished by their function.