Products in the logic output, slot type photointerrupter family integrate a light source and a matching photodetector in an opposed-facing orientation, together with supporting circuitry needed to make a binary (two-state) determination of whether or not an opaque object or material is present in the space between the emitter and receiver. They differ from transistor output devices of the same name by virtue of this additional receive-side processing, which simplifies application at some expense of application flexibility.