Here is the schematics of a fairly loud #MorseCode sounder. I built this for Berlin #MakerFaire 2018, where Berlin #hamradio clubs operated a joint booth and I served as Morse code + #GMA presenter. Something loud enough over the background noise of a faire was needed - this is it!
I've consistently found Morse code demonstrations a wonderful tool to attract people in a public situation: Everybody has heard of Morse code, but hardly anybody has witnessed it in action.