Valdemar Poulsen

Valdemar Poulsen (23 November 1869 – 23 July 1942) was a Danish engineer who developed a magnetic wire recorder called the telegraphone in 1898. He also made significant contributions to early radio technology, including the first continuous wave radio transmitter, the Poulsen arc, which was used for a majority of the earliest audio radio transmissions, before being supplanted by the development of vacuum-tube transmitters.