This circuit is from General Electric from the 80s, using a relay with high current contacts (20 A). The transistor admits equivalent, and any phototransistor can be used as a sensor.
The output current of this circuit reaches 12 mA. The zener diode determines the output voltage. The...
Found in Maxim's documentation from the 90's, this circuit uses an integrated from the time...
Found in a 1980s documentation, this circuit makes use of components from that time. Modern...