Originally, this circuit was created to monitor the liquid level in the reservoir of a car's windshield wiper. The circuit is from documentation from the 90s.
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...