One summer afternoon, as Bell was working in his workshop in Boston, he heard an almost inaudible twanging sound from his prototype telephone - a sort of crude harmonica with a clock-spring reed, a magnet and a wire. This was connected to a similar device in another room where his assistant Thomas Watson was working.
Watson had snapped the reed on one of the instruments and from the other device Bell had heard exactly the same sound. It was the first time in the history of the world that a complex sound had been carried along a wire, and reproduced perfectly at the other end.
