This filter was found in an 80's English publication. However, it can be implemented with modern operating systems. The circuit can tune frequencies in a range from 10,000 to 1.
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
This linear LED scale circuit was found in the February 1992 issue of Radio Electronics magazine. Note...
This circuit is from the owner's manual of the integrated circuits used. The manual is old, which...