Magnetic tape
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225828760
2008-07-15T16:18:09Z
Epbr123
1395162
Reverted edits by [[Special:Contributions/OrgasGirl|OrgasGirl]] to last version by CosineKitty (using [[WP:HG|Huggle]])
{{Refimprove|date=May 2008}}
[[Image:magtape1.jpg|thumb|7 inch reel of ¼ inch-wide audio recording tape, typical of consumer use in the 1950s-70s.]]
'''Magnetic tape''' is a medium for [[magnetic recording]] generally consisting of a thin magnetizable coating on a long and narrow strip of [[plastic]]. Nearly all recording tape is of this type, whether used for recording [[audio]] or [[video]] or for [[computer data storage]]. It was originally developed in Germany, based on the concept of [[Wire recording|magnetic wire recording]]. Devices that record and playback audio and video using magnetic tape are generally called [[tape recorder]]s and [[video tape recorder]]s respectively. A device that stores computer data on magnetic tape can be called a [[tape drive]], a tape unit, or a streamer.
Magnetic tape revolutionized the broadcast and recording industries. In an age when all [[radio]] (and later [[television]]) was live, it allowed programming to be prerecorded. In a time when [[gramophone record]]s were recorded in one take, it allowed recordings to be created in multiple stages and easily mixed and edited with a minimal loss in quality between generations. It is also one of the key enabling technologies in the development of modern [[computer]]s. Magnetic tape allowed massive amounts of data to be stored in computers for long periods of time and rapidly accessed when needed.
Today, many other technologies exist that can perform the functions of magnetic tape. In many cases these technologies are replacing tape. Despite this, innovation in the technology continues and tape is still widely used.
== Audio recording ==
[[Image:Kaseta magnetofonowa ubt.jpeg|thumb|[[Compact Cassette]] ]]
{{main|Magnetic tape sound recording}}
Magnetic tape was first invented for recording sound by [[Fritz Pfleumer]] in [[1928]] in [[Germany]], based on the invention of magnetic wire recording by [[Valdemar Poulsen]] in [[1898]]. Pfleumer's invention used an [[iron oxide]]([[Iron(III) oxide|Fe<sub>2</sub>O<sub>3</sub>]]) powder coating on a long strip of paper. This invention was further developed by the German electronics company [[AEG]], which manufactured the recording machines and [[BASF]], which manufactured the tape. In 1933, working for AEG, [[Eduard Schuller]] developed the ring shaped tape head. Previous head designs were needle shaped and shredded the tape. An important discovery made in this period was the technique of [[tape bias|AC biasing]] which dramatically improved the fidelity of the recorded audio signal.
Due to the international hostilities preceding [[World War II]], these developments were largely kept secret from the rest of the world. It was only after the war that Americans, particularly [[Jack Mullin]], [[John Herbert Orr]], and [[Richard H. Ranger]] were able to bring this technology out of Germany.
A wide variety of recorders and formats have developed since, most significantly [[reel-to-reel]] and [[Compact Cassette]].
== Video recording ==
{{main|Videotape}}
The practice of recoding and editing audio using magnetic tape rapidly established itself as an obvious improvement over previous methods. Many people saw the potential of making the same improvements in recording television. Television ("video") signals are, in principle, very similar to audio signals. The main difference is that video signals use much more [[bandwidth (signal processing)|bandwidth]] than audio signals. This meant that the existing audio tape recorders could not capture a video signal effectively.
Many people set to work on resolving this problem. Jack Mullin (working for Bing Crosby) and the BBC both created crude working systems that involved moving the tape across a fixed tape head at very fast speeds. Neither of these systems saw much use. It was the team at [[Ampex]], lead by [[Charles Ginsburg]], that made the breakthrough of using a spinning recoding head and normal tape speeds to achieve a very high head-to-tape speed that could record and reproduce the high bandwidth signals of video. The Ampex system was called [[2 inch Quadruplex videotape|Quadruplex]] and used 2 inch wide tape, mounted on reels like audio tape, and a wrote the signal in what is now called ''transverse scan''.
Later improvements by other companies, particularly [[Sony]], lead to the development of [[helical scan]] and the enclosure of the tape reels in an easy-to-handle [[Cartridge (electronics)|cartridge]]. Nearly all modern videotape systems use helical scan and cartridges. [[Videocassette recorder]]s are very common in homes and television production facilities though many functions of the VCR are being replaced. Since the advent of digital video and computerized video processing, [[optical disc]] media and [[digital video recorder]]s can now perform the same role as videotape. These devices also offer improvements like [[random access]] to any scene in the recording and "live" [[time shifting]] and are likely to replace videotape in many situations.
== Data storage ==
{{main|Magnetic tape data storage}}
The use of magnetic tape for [[computer data storage]] has been one of the constants of the computer industry. In all formats, a [[tape drive]] (or "transport" or "deck") uses precisely-controlled motors to wind the tape from one reel to another, passing a [[tape head]] as it does.
Magnetic tape was first used to record computer data in 1951 on the Eckert-Mauchly [[UNIVAC I]]. The recording medium was a thin strip of one half inch (12.65 mm) wide metal, consisting of nickel-plated bronze (called Vicalloy). Recording density was 128 characters per inch (198 micrometre/character) on eight tracks.
[[Image:Tapesticker.jpg|thumb|left|Small open reel of [[9 track tape]] ]]
[[IBM 7 track|Early IBM tape drives]] were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long u-shaped loops of tape. When active, the two tape reels thus fed tape into or pulled tape out of the vacuum columns, intermittently spinning in rapid, unsynchronized bursts resulting in visually-striking action. Stock shots of such vacuum-column tape drives in motion were widely used to represent "the computer" in movies and television.
[[Image:Quarter-Inch Cartridges.jpg|thumb|right|[[Quarter inch cartridge]]s, a data format commonly used in the 1980s and 1990s.]]
Most modern magnetic tape systems use reels that are much smaller than the old 10.5 inch open reels and are fixed inside a cartridge to protect the tape and facilitate handling. Many late 1970s and early 1980s home computers used [[Compact Cassette]]s encoded with the [[Kansas City standard]]. Modern cartridge formats include [[Linear Tape-Open|LTO]], [[Digital Linear Tape|DLT]], and [[Digital Data Storage|DAT/DDC]].
Tape remains a viable alternative to disk due to its lower cost per bit. Though the areal density is lower than for disk drives, the available surface on a tape is far greater. The highest capacity tape media are generally on the same order as the largest available disk drives (about 1 [[Terabyte|TB]] in 2007.) Tape has historically offered enough advantage in cost over disk storage to make it a viable product, particularly for [[backup]], where media removability is also important. The rapid improvement in disk storage density and price, coupled with arguably less-vigorous innovation in tape storage, has reduced the market share of tape storage products.
In 2002, [[Imation]] received an [[US$]]11.9 million grant from the U.S. [[National Institute of Standards and Technology]] for research into increasing the data capacity of magnetic tape.<ref>{{cite web|title=The Future of Tape: Containing the Information Explosion|url=http://www.imation.com/about_imation/company_info/50years/future_tape.html|accessdate=19 September|accessyear=2006}}</ref>
==References==
<references />
{{FOLDOC}}
== External links ==
{{commons|Tape|Magnetic tape}}
*[http://web.archive.org/web/20040603152849/http://www.tvhandbook.com/History/History_recording.htm History of Tape Recording Technology]
* [http://www.vidipax.com/audiogd/index.html VidiPax Audio Format Guide]
{{Magnetic storage media}}
[[Category:Audio storage]]
[[Category:Computer storage tape media]]
[[Category:Magnetic devices]]
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