Indicated for discriminators adjustment in FM and VHF receivers, this circuit was found in a 90s 73 magazine for radio amateurs. The operational amplifier can be a general-purpose type.
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...