This circuit was found in a Popular Electronics from the 90s. The circuit uses a general purpose JFET. The coils depend on the signal range that must be amplified.
Here we show how two 4017s can be cascaded to count above 10. The circuits are driven by a square...
The circuit in the figure represents a typical application of a phototransistor exciting a relay...
This circuit, in fact, what it does is a reactivation of the batteries through a brief pulsating...