Magnetic tape is a medium for magnetic recording, made of a thin,
magnetizable coating on a long, narrow strip of plastic film. It was
Germany in 1928, based on magnetic wire recording.
Devices that record and play back audio and video using magnetic tape
are tape recorders and video tape recorders. A device that stores
computer data on magnetic tape is known as a tape drive.
Magnetic tape revolutionized broadcast and recording. It allowed
radio, which had always been broadcast live, to be recorded for later
or repeated airing. It allowed gramophone records to be recorded in
multiple parts, which were then mixed and edited with tolerable loss
in quality. It was a key technology in early computer development,
allowing unparalleled amounts of data to be mechanically created,
stored for long periods, and rapidly accessed.
In recent decades, other technologies have been developed that can
perform the functions of magnetic tape. In many cases, these
technologies have replaced tape. Despite this, innovation in the
technology continues, and
IBM continue to produce new
magnetic tape drives.
Over time, magnetic tape made in the 1970s and 1980s can suffer from a
type of deterioration called sticky-shed syndrome. It is caused by
hydrolysis of the binder in the tape and can render the tape
2 Audio recording
3 Video recording
4 Data storage
5 See also
7 External links
The oxide side of a tape is the surface that can be magnetically
manipulated by a tape head. This is the side that stores the
information, the opposite side is simply a substrate to give the tape
strength and flexibility. The name originates from the fact that the
magnetic side of most tapes is typically made of iron oxide though
chromium is used for some tapes. An adhesive binder between the oxide
and the substrate holds the two sides together.
Magnetic tape was invented for recording sound by
Fritz Pfleumer in
1928 in Germany, based on the invention of magnetic wire recording by
Oberlin Smith in 1888 and
Valdemar Poulsen in 1898. Pfleumer's
invention used a ferric oxide (Fe
3) 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 tended to shred the tape.
An important discovery made in this period was the technique of AC
biasing, which improved the fidelity of the recorded audio signal by
increasing the effective linearity of the recording medium.
Due to the escalating political tensions, and the outbreak of World
War II, these developments 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, the nature was not
discovered until the Allies acquired captured German recording
equipment as they invaded Europe in the closing of the war. It was
only after the war that Americans, particularly Jack Mullin, John
Herbert Orr, and Richard H. Ranger, were able to bring this technology
Germany and develop it into commercially viable formats.
A wide variety of recorders and formats have developed since, most
significantly reel-to-reel and Compact Cassette.
The practice of recording and editing audio using magnetic tape
rapidly established itself as an obvious improvement over previous
methods. Many saw the potential of making the same improvements in
recording television. Television ("video") signals are similar to
audio signals. A major difference is that video signals use more
bandwidth than audio signals. Existing audio tape recorders could not
practically capture a video signal. Many set to work on resolving this
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 system saw much use. It
was the team at Ampex, led by Charles Ginsburg, that made the
breakthrough of using a spinning recording 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 Quadruplex and used 2-inch-wide (51 mm) tape, mounted on
reels like audio tape, which wrote the signal in what is now called
VHS helical scan head drum. Helical and transverse scans made
possible to increase the data bandwidth to the necessary point for
recording video on tapes, and not just audio.
Later improvements by other companies, particularly Sony, led to the
development of helical scan and the enclosure of the tape reels in an
easy-to-handle videocassette cartridge. Nearly all modern videotape
systems use helical scan and cartridges.
Videocassette recorders used
to be common in homes and television production facilities, but many
functions of the VCR have been replaced with more modern technology.
Since the advent of digital video and computerized video processing,
optical disc media and digital video recorders 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 have replaced videotape in many situations.
Magnetic tape data storage
In all tape formats, a tape drive uses motors to wind the tape from
one reel to another, passing over tape heads to read, write or erase
as it moves.
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.
Small open reel of 9 track tape
IBM 7 track tape drives were floor-standing and used vacuum
columns to physically buffer long U-shaped loops of tape. The two tape
reels visibly fed tape through the columns, intermittently spinning
the reels 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
Quarter inch cartridges, a data format commonly used in the 1980s and
Most modern magnetic tape systems use reels that are much smaller than
the 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 Cassettes, encoded with the Kansas
City standard, or several other "standards" such as the Tarbell
Cassette Interface. Modern cartridge formats include LTO, DLT, and
Tape remains a viable alternative to disk in some situations due to
its lower cost per bit. This is a large advantage when dealing with
large amounts of data. Though the areal density of tape is lower than
for disk drives, the available surface area on a tape is far greater.
The highest capacity tape media are generally on the same order as the
largest available disk drives (about 5 TB in 2011). Tape has
historically offered enough advantage in cost over disk storage to
make it a viable product, particularly for backup, where media
removability is necessary.
Tape has the benefit of a comparatively long duration during which the
media can be guaranteed to retain the data stored on the media.
Fifteen (15) to thirty (30) years of archival data storage is cited by
manufacturers of modern data tape such as
Linear Tape-Open media.
Imation received a US$11.9 million grant from the U.S.
National Institute of Standards and Technology
National Institute of Standards and Technology for research into
increasing the data capacity of magnetic tape.
IBM announced that they had been able to record 148
gigabits per square inch with magnetic tape media developed using a
new vacuum thin-film forming technology able to form extremely fine
crystal particles, allowing true tape capacity of 185 TB.
^ a b "
Sony develops magnetic tape technology with the world's
highest*1 areal recording density of 148 Gb/in2".
Retrieved 4 May 2014.
^ "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. Retrieved 12 December 2017.
^ "The Future of Tape: Containing the Information Explosion" (PDF).
Retrieved 12 December 2017.
^ Fingas, Jon (4 May 2014). "Sony's 185TB data tape puts your hard
drive to shame". Engadget. Retrieved 4 May 2014.
This article is based on material taken from the Free On-line
Dictionary of Computing prior to 1 November 2008 and incorporated
under the "relicensing" terms of the GFDL, version 1.3 or later.
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