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.
The purpose of this 1967 Philips circuit is to produce a rectangular signal from a sharp pulse....
This very low current circuit with the ICM7860 was found in the April 1995 Electronics Now...
We found this circuit in an old American documentation. The operational amplifier is not common...