Found in a 90s Popular Electronics, this circuit triggers a load from the audio signal applied to its input. The controlled load depends on the MOSFET.
We found this circuit in an American 80's documentation. The circuit can be adapted to function as a...
This 80's circuit, suggested in Texas Insrtruments documentation, uses a Hall effect sensor. The...
This interesting benchtop circuit was found in the May 1977 issue of Radio Electronics magazine. The...