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Foto: Compact Disc (C) KamenWeb.deThe Compact Disc (CD for short) is an optical storage device that was introduced by Philips/PolyGram and Sony in the early 1980s for the digital storage of music and was intended to replace the record. The format of the compact disc was later expanded to not only store music (CD-DA). Since then, it has also been used as a CD-ROM to store data for computers.

CD viewed with a scanning electron microscope (protective coating removed) In the 1970s, technicians from many electronics companies researched digital audio recording. The first prototypes were based on magnetic storage media, such as the classic audio cassette. The first device on the market in 1977 was an extension of Sony’s Betamax video recorder to include an analogue-to-digital or digital-to-analogue converter (PCM modulator or demodulator). In this case, the video recorder records the PCM signal instead of a video signal, which – due to appropriate coding in lines or images (frames) – looks like a video signal from the point of view of a video recorder. The bulky device and the background noise during recording could not convince consumers. Sony developed special procedures to eliminate the noise. In order to test these methods, secret recordings were made during a rehearsal of a Herbert von Karajan concert in September 1978. Karajan was later invited by Sony to assess the recordings.

Light diffraction on a compact disc At the same time, the Philips company was working on the optical recording of image signals, which was to revolutionize video technology. i.a. the video disc was presented at the Funkausstellung in Berlin, which was about the size of an LP and played back by a correspondingly large player. The idea of ​​using this technology for digital sounds soon developed. Both companies were suddenly faced with a problem. They had planned the new optical data carrier (laser disc), similar to the record, with a diameter of 30 cm. When recording moving images, they could fit about 30 minutes of video material on it. With audio data, however, the capacity was sufficient for 13 hours and 20 minutes. Sony knew that the music industry’s business model would collapse if they were to market such volumes of music to consumers. After the compact cassette (audio cassette) had been developed by the company Philips alone in 1963, both companies now tried to bring about a common standard. The diameter of the CD, which is decisive for the playing time, was justified by the Philips management as follows: The compact cassette was a great success, the CD shouldn’t be much larger. The Compact Cassette had a diagonal of 11.5 cm, the engineers made the CD 0.5 cm larger. All sorts of modern legends surround the determination of these parameters; one of the most popular is the following:

After some differences, Sony suggested that the new CD should at least cover Ludwig van Beethoven’s Ninth Symphony in full. This proposal hung with Sony’s then-Vice President Norio ?ga[1] together, who was a trained opera singer and had always wished to be able to hear Beethoven’s Ninth without having to switch discs. ?ga’s favorite version, conducted by Herbert von Karajan, lasts 66 minutes; the technicians stuck to Wilhelm Furtwängler’s version, which was the longest available at the time. The recording from 1951 has a playing time of exactly 74 minutes. 74 minutes meant the diameter of the optical data carrier was 12 cm. The developers at Philips reacted with skepticism, since such a large disc would not fit in the suit pocket. Sony developers then measured suits from all over the world, with the result that there is room for 12 cm everywhere. Beethoven had thus set a new standard.

A similar version of the story is officially circulated by Philips; however, the influence of Beethoven on the CD playing time is also sometimes disputed.

In 1980, Philips and Sony established the “Red Book” standard for audio recording. The diameter of the inner hole of the CD (15 mm) was determined more or less by chance by the Dutch Philips developers. The smallest coin in the world at the time, the Dutch ten cent piece (the so-called Dubbeltje), served as a benchmark, which a developer had with him when determining the diameter. The CD was presented to the public for the first time at the 1981 radio exhibition in Berlin. The following year, on August 17, 1982, the world’s first industrial production of the last ABBA album The Visitors began in Langenhagen near Hanover, in the production facilities of what was then Polygram, even before the first mass-produced album on October 1, 1982 CD players could be offered in the market. In 1983, a compact disc cost between 30 and 45 DM, around 700 titles were available. In the same year, around 70,000 CD players were sold in the Federal Republic of Germany, costing between 650 and 1,800 DM in 1984. In 1988, 100 million audio CDs were produced worldwide. From this year there were systems with which CDs could be burned and no longer had to be injected as before…

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