[MrBra]

mechanical compressive wave ,traveling at the speed of sound? Why do u introduce these? What has sound to do with my example? Imagine the stick not tapping on ground but just getting close. to it. Not an audio, but a visual way for the receiver to tell the 2 different singnal states. Then he'd grab his end of the stick and do the same. I am sure what you say is correct by itself but.. it feels there is just something from it that doesn't fit with my example.. Edit: reading again your comment and trying to understand what you say.. if i get it right then it's totally misleading to call it "speed of sound": it should be called speed of mechanical compressive waves