This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics magazine. The source must be symmetrical. The capacitors can be changed for other frequencies.
Found in an 1989 R-E Experimenters Handbook, this circuit produces several sound effects that can...
This circuit triggers a load that depends on the characteristics of the transistor when we touch...
This circuit uses a GE optical coupler. Equivalents can be tried. The circuit is from the GE...