Designed for applications requiring ample clearance of the sensing body and the moving object, the OPB819 gap sensor is suitable for industrial controls for monitoring track motion. This ultra-wide gap sensor provides two mounting holes for easy and secure placement and individual LED and phototransistor wire connections measure 24" in length. The unit consists of an infrared emitting diode and a NPN phototransistor mounted in a plastic housing on opposite sides of a 31.75-mm wide slot. Phototransitor switching initiates when an opaque object passes through the slot. Price is $4 each/1,000.