Morse key, c 1850-1870.
© Science Museum / Science & Society Picture Library
This early Morse key was used by the Post Office Telegraph Service. This key, which functions as a simple switch, is quite cumbersome in shape and size. As Morse keys evolved, they became increasingly sophisticated, developing into carefully engineered instruments. The Morse system required a skilled operator using a Morse key to interrupt the current from a battery into a wire circuit. At the other end a buzzer converted the electrical signals into sounds, which were manually converted back into letters by a trained operator.