This circuit is from the time when photos were revealed in darkrooms. We found it in a 1968 Electronics World. The circuit can be used for other purposes.
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....