This noise limiter for low intensity signals was found in a 73 magazine for radio amateurs from the 90's. The circuit is for signals from 10 mV to 1 V amplitude.
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...