The Optosupply OSNG5134A is a surface-mount, four-pin Phototransistor Optocoupler. It is designed to provide isolation between two parts of a circuit while allowing current to flow between two circuits. It can be used in various applications as a signal isolator, a sensor interface, level-shifting, communication interface circuits, and more. The four pins include an Emitter, Detector, Ground and Vcc pins. The Optosupply OSNG5134A features a gain of 200 to 6500, a maximum current transfer ratio of 10mA, and a forward voltage of 1.25 V. It is also RoHS-compliant and UL-recognized.