We've Come a Long Way From This

I came across a can phone in a creative arts magazine and It got me thinking about technology and communications. This can phone would have been something of a phenomenon in the early days of the telegraph. An entire theory developed around this very artifact which pretty much revolutionized telecommunications. Just think.....two cans and a string!! [Sound waves, signal transduction, converters, physics, etc.] Two Cans and a String!!!