AC/DC input opto for line-voltage sensing
The H11AA4VM is a single-channel optoisolator from onsemi that accepts both AC and DC input — the AC input capability lets it sense mains-level AC signals directly through a series resistor, saving a bridge rectifier on the primary side. Rated for 4170Vrms isolation, it bridges the safety gap between line-voltage circuits and low-voltage control logic in a 6-DIP through-hole package.
Transistor output with base access
The output is a phototransistor with a separate base terminal (6-DIP pinout), giving you the option to bias the base for faster switching or to connect a base-emitter resistor for noise immunity — handy in industrial environments where long sense wires pick up hash. Minimum current transfer ratio is 100% at 10 mA forward current, and the output can sink up to 50 mA continuous with a maximum Vce(sat) of 400 mV.