In the figure we have two circuits of limiters that provide the cut of the negative peaks of a signal. The circuit is from an 80's telecom documentation being adaptable on common receivers.
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....