Poulsen's Telegraphone, 1903.
© Science Museum / Science & Society Picture Library
Patented in 1898 by the Danish electrical engineer and inventor Valdemar Poulsen (1869-1942), the Telegraphone was the first telephone answering machine and laid the foundations of magnetic recording. Poulsen discovered that he could record sound by speaking into a microphone attached to a magnet which was moved slowly acros a thin wire. As the wire became magnetised, a trail of sound patterns was recorded. However, poor sound quality prevented the Telegraphone from achieving commercial succes and Poulsen became disheartened. In the 1930s the Germans adapted his invention for military use, exchanging the wire for magnetic coated plastic tape. This simultaneously improved sound quality and enabled reuse. After World War II, the machine was adopted by the entertainment industry and experienced great popularity.