Valdemar Poulsen (1869-1942) was a Danish electrical engineer and inventor. Poulsen invented the telegraphone for recording telephone conversations and the Poulsen Arc Transmitter.
Poulsen Arc Transmitter
The arc transmitter which contrary to all previous types of radio transmitters - generated continuous radio waves. The transmitter was invented by the Danish engineer Valdemar Poulsen in 1902.
Biography and patent drawings.
Development of Electromagnetic Tape Recording
Contributions to sound recording made by Valdemar Poulsen.
History of Sound Recording