Reversible telephone

Europe discovered Graham Bell’s telephone at the Universal Exposition of 1878. The scientific instrument maker Antoine Breguet had presented the device to the Académie des Sciences a few months earlier. Although initially perplexed by the simplicity of its principle, scientists were fascinated by Bell’s telephone. It was now possible to hear, understand and even recognise someone’s voice at a distance of several thousand kilometres, linked merely by a single telegraph wire. The voice makes a sheet of metal vibrate in front of a magnet surrounded by electric wire. The membrane makes the magnet move, which modifies the magnetic field and creates an electric current. The principle is reversed and the voice is reproduced at the other end of the line. Antoine Breguet’s widow, Marie Breguet, donated these telephones to the Conservatoire des Arts et Métiers in 1884.