Found in an American documentation from the 90s, this circuit uses small low voltage lamps (6 to 12 V0. The circuit can be adapted to use LED indicators.
This simple expandable circuit was obtained from a Popular Electronics from the 80's. The supply...
The frequency of the LC resonant circuit must be the same as that of the crystal and the JFET...
This circuit was obtained in a Popular Electronics of 1991. The magazine no longer exists, but the...