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.
This circuit can operate in a 100 dB range with signals of up to 100 MHz frequencies. Similar...
This audio level indication system for microphones was found in Radio Electronics from the 90s....
This circuit was found in a 90’s Electronic Design. The circuit uses components that are still...