Transistor output optoswitch isocom h21a1 a single transistor output optoswitch which consists of a gallium arsenide infrared emitting diode and an npn silicon photo transistor mounted in a polycarbonate housing high gain 3mm gap between led and detector typical applications include copiers printers facsimiles record players cassette decks and optoelectronic switches isocom h21a1a3 transistor output optoswitch