Medium used to store data in the form of magnetic fields
7-inch reel of ¼-inch-wide audio recording tape, typical of consumer use in the 1950s–70s.
Magnetic tape is a medium formagnetic storage made of a thin, magnetizable coating on a long, narrow strip ofplastic film. It was developed in Germany in 1928, based on the earliermagnetic wire recording from Denmark. Devices that use magnetic tape can with relative ease record and play back audio, visual, and binary computer data.
Magnetic tape revolutionizedsound recording and reproduction and broadcasting. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. Since the early 1950s, magnetic tape has been used with computers to store large quantities of data and is still used for backup purposes.
Magnetic tape begins to degrade after 10–20 years and therefore is not an ideal medium for long-term archival storage.[1] The exception is data tape formats likeLTO which are specifically designed for long-term archiving.[2]
Information in magnetic tapes is often recorded in tracks which are narrow and long areas of information recorded magnetically onto the tape, which are separate from each other and often spaced apart from adjacent tracks. Tracks are often parallel to the length of the tape, in which case they are known as longitudinal tracks,[3][4] or diagonal relative to the length of the tape inhelical scan.[5] There are also transverse scan and arcuate scanning, used inQuadruplex videotape.Azimuth recording is used to reduce or eliminate the spacing that exists between adjacent tracks.
While good for short-term use, magnetic tape is highly prone to disintegration. Depending on the environment, this process may begin after 10–20 years.[1]
Over time, magnetic tape made in the 1970s and 1980s can suffer from a type of deterioration calledsticky-shed syndrome. It is caused byhydrolysis of the binder in the tape and can render the tape unusable.[6]
Since the introduction of magnetic tape, other technologies have been developed that can perform the same functions, and therefore, replace it. Such as for example, hard disk drives in computers replacing cassette tape readers such as theAtari Program Recorder and theCommodore Datasette for software,[7] CDs and MiniDiscs replacing cassette tapes for audio, and DVDs replacing VHS tapes. Despite this, technological innovation continues. As of 2014[update]Sony andIBM continue to advance tape capacity.[8]
Magnetic tape was invented for recording sound byFritz Pfleumer in 1928 in Germany.[9]
Because of escalating political tensions and the outbreak of World War II, these developments in Germany were largely kept secret. Although the Allies knew from their monitoring of Nazi radio broadcasts that the Germans had some new form of recording technology, its nature was not discovered until the Allies acquired German recording equipment as they invaded Europe at the end of the war.[10] It was only after the war that Americans, particularlyJack Mullin,John Herbert Orr, andRichard H. Ranger, were able to bring this technology out of Germany and develop it into commercially viable formats.Bing Crosby, an early adopter of the technology, made a large investment in the tape hardware manufacturerAmpex.[11]
A wide variety of audiotape recorders and formats have been developed since. Some magnetic tape-based formats include:
AVHS helical scan head drum. Helical and transverse scans made it possible to increase the data bandwidth to the necessary point for recording video on tapes, and not just audio.
Videotape is magnetic tape used for storing video and usuallysound in addition. Information stored can be in the form of either ananalog ordigital signal. Videotape is used in bothvideo tape recorders (VTRs) and, more commonly,videocassette recorders (VCRs) andcamcorders. Videotapes have also been used for storing scientific or medical data, such as the data produced by anelectrocardiogram.
Tape was an important medium forprimary data storage in early computers, typically using large openreels of7-track, later9-track tape. Modern magnetic tape is most commonly packaged incartridges andcassettes, such as the widely supportedLinear Tape-Open (LTO)[12] andIBM 3592 series. The device that performs the writing or reading of data is called atape drive.Autoloaders andtape libraries are often used to automate cartridge handling and exchange. Compatibility was important to enable transferring data.
Tape data storage[13] is now used more for system backup,[14] data archive and data exchange. The low cost of tape has kept it viable for long-term storage and archive.[15]
^"Magnetic Materials"(PDF).Memory of the World: Safeguarding the Documentary Heritage. A guide to Standards, Recommended Practices and Reference Literature Related to the Preservation of Documents of All Kinds. UNESCO. 1998. CII.98/WS/4. Retrieved12 December 2017.
