Scientific research applied to the telephone transmitter and receiver

Let us recall a scene at the Centennial Exhibition in Philadelphiain 1876. Across a room had been strung wires connecting crude instruments, at one end of the room a transmitter and at the other end of the room a receiver. Dam Pedro, Emperor of Brazil, takes up the receiver and listens while Alexander Graham Bell speaks into the transmitter. The Emperor, astonished at hearing Mr. Bell's voice in the receiver, exclaims in amazement, “My God, it talks.”