The HOA1887 series consists of an infrared emitting diode facing an NPN silicon phototransistor (HOA1887- 011, - 012) or photodarlington (HOA1887- 013) encased in a black thermoplastic housing. Detector switching takes place whenever an opaque object passes through the slot between emitter and detector. The side mounting package is useful in applications in which the interruptive element is parallel to the mounting plane. Both emitter and detector have a 0.010 in.(0.25 mm) x 0.60 in(1.52 mm) vertical aperture. This feature is ideal for use in applications in which maximum position resolution is desired.