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 with a constant speed 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 can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.
Poulsen obtained a Telegraphone Patent in 1898. Poulsen developed an Arc Converter in 1908, referred to as the "Poulsen Arc Transmitter". A stamp was issued in honor of Poulsen in 1969.
Poulsen, Valdemar, "US661619 Method of Recordings and Reproducing Sounds or Signals (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=661619.WKU.&OS=PN/661619&RS=PN/661619)". Magnetic Tape Recorder.
ValdemarPoulsen, son of a Danish High Court judge was born 23rd November 1869 in Copenhagen.
Poulsen's arc as a generator of continuous waves differed from the usual arc since it burned in an atmosphere of a hydrocarbon gas in a strong transverse magnetic field.
Poulsen's great discovery was the effect of a hydrogen atmosphere which by cooling the arc increased the steepness of its characteristic curve, and also the use of very powerful magnetic field which enabled him to get a high terminal voltage.
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