The integrated circuit used in this detector is uncommon today. We found it in a documentation from the 70s. Detection is done by an optical camera with LEDs and a photo sensor.
Found in an EDN from the 80's, this circuit makes use of an operational one of the time. The...
This circuit can either directly supply a piezoelectric transducer (BZ) or a stage with a...
Only for reference this is a circuito f a commercial receiver of the year 1958. The circuit uses...