The ITR9606-F consist of an infrared emitting diode and an NPN silicon phototransistor,encased side-by-side on converging optical axis in a black thermoplastic housing,The phototransistor receives radiation from the IRED only .This is the normal situation.But when an object is in between , phototransistor could not receives the radiation.For additional component information , please refer to IR928-6C-F and PT928-6C-F