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 is from Radio Electronics from the 90s. It supplies a voltage between 800 V and 2 000...
This audio detector circuit can be used for cable identification. We found it in a Popular...
This highly sensitive circuit was found in a 1967 General Electric SCR manual. Equivalent...