This active tone control circuit was found in American documentation from the 90's. The transistor can be general purpose or low noise with high gain.
This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can...
This voice scrambler and descrambler circuit was found in a Radio Electronics from July 1963....
Using a 4017 as a base, this circuit from a 1990s Popular Electronics generates low-frequency...