The LTR-4206 series consist of a NPN silicon phototransistor mounted in a lensed, clear plastic, end looking package. The lensing effect of the package allows an acceptance half angle of 10 measured from the optical axis to the half power point. This series is mechanically and spectrally matched to the LTE-4206 series of infrared emitting diodes. The LTR-4206E is a special dark plastic package that cut the visible light and suitable for the detectors of infrared application.