Valdemar Poulsen was a Danish engineer who invented the magnetic recorder in 1898. His ideas were the basis of magnetic recording and led to crucial developments in communications and computer technology. Born in Copenhagen on November 23, 1869, Poulsen exhibited an early interest in science. He later studied various aspects of science in depth, though he never earned a degree. Around 1890, Poulsen began working in local machine shops, finally joining the Copenhagen Telephone Company as an assistant engineer in its technical section in 1893. It was while working there, at the age of 20, that he developed the telegraphone, a machine that recorded sounds magnetically on a wire.

The concept of recording sounds magnetically had originated with the British inventor Oberlin Smith (1840-1926) in 1888, but Poulsen put that concept into practice ten years later. Smith's ideas had involved using "tapes" of fabric containing iron filings, but Poulsen's device used magnetized steel piano wire...