The 4N35TVM is a single-channel optoisolator from onsemi with a DC infrared LED input and a phototransistor output that brings the base terminal out to pin 6. The 4170Vrms isolation rating lets it bridge a noisy high-voltage domain — think 24 VDC industrial sensors talking to a 3.3 V or 5 V microcontroller — without a ground loop. The output transistor's base is brought out separately, which is the key difference from a simpler optocoupler like the 4N35VM: you can add a base resistor to tailor the switching speed or use the transistor in a Darlington configuration for higher gain. The 300 mV maximum Vce(sat) keeps the output voltage drop low when the transistor is fully on, so it can drive a 5 V logic input directly or switch a small relay with a series resistor.
Temperature range and package — board-fit decisions
That covers outdoor telecom cabinets, factory-floor PLC I/O modules, and auxiliary circuits in engine bays where ambient can hit 85°C. The through-hole 6-DIP package (0.400", 10.16mm) is a standard 300-mil body — it fits the same footprint as the 4N35VM and 4N28M. The tube delivery is typical for DIP parts; plan for manual or wave-solder assembly. The 30 V maximum output voltage limits the collector load to low-voltage rails — 5 V, 12 V, or 24 V logic supplies are fine, but you cannot switch a 48 V or 120 V load directly. The 60 mA maximum forward current gives headroom for driving the LED at 10–20 mA with a series resistor; the typical forward voltage is 1.18 V.