The CSM165-4 from ISOCOM is a Space Qualified Optocoupler with Forward Voltage 1.6 V, Continuous Current 50 mA, Collector-Emitter Dark Current 0.1 uA, Collector-Emitter Saturation Voltage 0.22 V, Operating Temperature -55 to 125 Degree C. More details for CSM165-4 can be seen below.