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.
This circuit was found in a 1992 documentation and has excellent sensitivity, using components that...
This practical idea from a 1992 documentation shows how to count the turns of a winder using a...
In this circuit from the 60s, the power supply is made with 22.5 V, which is the voltage of the...