Vishayisocom transistordarlington output optoisolators isocom tlp621 4x quad transistor output optoisolator consisting of infrared leds and npn silicon photo transistors in space efficient dual in line plastic packages 10mm lead spread high density mounting surface mount high resolution voltage used in computer terminals industrial systems controllers measuring instruments and signal transmission between systems of different potentials and impedances isocom tlp621 4x quad transistor