This sound intensity meter was found in a 90s Elektor. The circuit uses an integrated device from the time that is not common today. The indicator is a milliammeter.
This circuit maintains on a flashing LED at a frequency determined by the capacitor. The...
This circuit controls loads powered by the power grid, remembering that it is a half wave...
This two competitor version of the game is shown below and uses lamps as indicators. You can...