A small and durable LED thrubeam pair, designed for precise detection in restricted and abusive areas. Specially selected Light Emitting Diodes and photodetectors are mounted in stainless steel bodies and offered as the tiniest industrial pair in the photoelectric sensing market. The infrared energy from the LED light source can be detected by the photodetector from as far as 6 in. away and can be modulated to defeat the effects of ambient light. In addition, the filter in the photodetector blocks visible light to the sensor. Solid state components and rugged construction assure the user of trouble-free operation and long life.