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.
The purpose of this circuit is to allow common analog multimeters to measure low resistances, on...
This is the circuit of the N-201 commercial multimeter of the analog type. The circuit is from...
This receiver was found in the Radio Electronics magazine of March 1953. It tunes to the medium wave...