This super regenerative detector circuit was found in an English documentation from 1963. The coil is frequency compliant. The transistors are germanium of the time.
With a touch of the sensor wire X1, which can also be a pressure switch, the LED lights for a time...
This alarm with automatic shutoff was found in the April 1975 Radio Electronics magazine. The...
This Colpitts crystal oscillator was found in an American publication for amateurs in the 1980s....