The 4N25 Optocoupler (also known as an optoisolator) is an electronic component that allows electrical signals to be transmitted between two isolated circuits using light. This family includes the N25, 4N26, 4N27, 4N28. Each optocoupler consists of gallium arsenide infrared LED and a silic damage to the device. Functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sec. 4N25 belongs to one of the most famous families of optocouplers. It contains a light e itting diode optically coupled to a photo-transistor. Response time, tr, is typically 3 ge in Tube packaging with. Agilent 4N25 Phototransistor Optocoupler General Purpose Type Data Sheet Ordering Information Specify part number followed by Option Number (if desired). 4N25-XXX Option Number 060 = VDE0884 Option W00 = 0.