Valdemar Poulsen

Valdemar Poulsen
Valdemar Poulsen (c. 1898)
Born	23 November 1869 Copenhagen
Died	23 July 1942(1942-07-23) (aged 72)
Nationality	Danish
Engineering career
Projects	magnetic wire recorder

Valdemar Poulsen (23 November 1869 – 23 July 1942) was a Danish engineer who made significant contributions to early radio technology. He developed a magnetic wire recorder called the telegraphone in 1899 and the first continuous wave radio transmitter, the Poulsen arc transmitter, in 1903, which was used in some of the first broadcasting stations until the early 1920s.

He was born on 23 November 1869 in Copenhagen.

The magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his telegraphone. Magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head (which may be the same as the recording head) can then pick up the changes in the magnetic field from the tape and convert them into an electrical signal.

Poulsen obtained a Telegraphone Patent in 1898, and with his assistant, Peder O. Pedersen, later developed other magnetic recorders that recorded on steel wire, tape, or disks. None of these devices had electronic amplification, but the recorded signal was easily strong enough to be heard through a headset or even transmitted on telephone wires. At the 1900 World's Fair in Paris, Poulsen had the chance to record the voice of Emperor Franz Josef of Austria which is believed to be the oldest surviving magnetic audio recording today.