This circuit was found in an American 1980s documentation. The transistorized step is the receiver's last IF and the diode is the receiver's existing detector.
July 2017 - Microchip's new MCP9V91 operational amplifiers with input offset and low drift voltage...
When the sensor, an ordinary photo-transistor, receives light, the relay closes its contacts. The...
Found in a 1964 Electronic Design, this circuit suppresses arcs that occur in contacts when a...