This circuit is an improvement over the previous one, using the same capacitor system as a sensor. We also found it in Radio Electronics from the 80s.
This circuit uses a contactor having been found in a 1987 publication. More modern equivalent...
Only for reference this is a circuito f a commercial receiver of the year 1958. The circuit uses...
This astable multivibrator configuration causes two LEDs to alternately flash at a frequency...