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Magnetic tape

Fritz Pfleumer, 1928

Magnetic tape was first patented by the German engineer Fritz Pfleumer in 1928, based on the invention of the magnetic wire by Valdemar Poulsen in 1898.
In 1932 AEG took up his idea and began manufacture of the machine calling it the Magnetophon while BASF produced the tape. The first public recording using the AEG Magnetophon was Nov. 19, 1936, with the London Philharmonic orchestra conducted by Sir Thomas Beecham at BASF's own concert hall in Ludwigshaven (sound excerpt).


It was not used to record data until 1951 on the Mauchly-Eckert
UNIVAC I. The recording medium was a 1/2 inch wide thin band of
nickel-plated bronze. Recording density was 128 characters per inch on eight tracks at a linear speed of 100 ips, yielding a data rate of
12,800 characters per second. Making allowance for the empty space
between tape blocks, the actual transfer rate was around 7,200
characters per second.

UNIVAC I - Tape Units, 1951

IBM computers from the 1950s used oxide-coated tape similar to that used in audio recording, and IBM's technology soon became the de facto industry standard. Magnetic tape was half an inch wide and wound on removable reels 10.5 inches in diameter. Different lengths were available with 2400 feet and 4800 feet being common.

In 1936 the German National Court declared that Pfleumer's patent
was nul and void because his idea of coating paper tape with iron dust was covered in Poulsen's original patents of 1898 and 1899 - further proof that Valdemar Poulsen stands alone as the inventor of all magnetic recording.

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