Magnetic tape

Compact Cassette

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
₂O
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, at the time a division of IG Farben, 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. Another 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 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.[3] 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 and develop it into commercially viable formats. Bing Crosby, an early adopter of the technology, made a large investment in the tape hardware manufacturer Ampex.[4]

A wide variety of audio tape recorders and formats have been developed since, most significantly reel-to-reel and Compact Cassette.

Digital recording to flash memory and hard disk has largely supplanted magnetic tape for most purposes. However tape as a verb and as a noun has remained the common parlance for the recording process.

Some magnetic tape-based formats include:

• Fidelipac
• Stereo-Pak
• Perforated (sprocketed) film audio magnetic tape (sepmag, perfotape, sound follower tape, magnetic film)
• 8-track tape
• Compact Cassette
• Elcaset
• RCA tape cartridge
• Mini-Cassette
• Microcassette
• Picocassette
• NT (cassette)
• ProDigi
• Digital Audio Stationary Head
• Digital Audio Tape
• Digital Compact Cassette

A 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.

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 the video signals used by television. 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 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 high 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 transverse scan.

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 the ability to pause a live program and have replaced videotape in many situations.

Some magnetic tape-based formats include:

Small open reel of 9 track tape

Magnetic tape was first used to record computer data in 1951 on the Eckert-Mauchly UNIVAC I. The system's UNISERVO I tape drive used a thin strip of one half inch (12.65 mm) wide metal, consisting of nickel-plated bronze (called Vicalloy). Recording density was 100 characters per inch (39.37 characters/cm) on eight tracks.[5]

Early IBM 7 track tape drives were floor-standing and used vacuum columns to mechanically buffer long U-shaped loops of tape. The two tape reels visibly fed tape through the columns, intermittently spinning 10.5 inch open 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 mainframe computers in movies and television.

Quarter inch cartridges, a data format commonly used in the 1980s and 1990s.

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 alternate encodings. Modern cartridge formats include LTO, DLT, and DAT/DDC.

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.

In 2002, Imation received a 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.[6]

Linear Tape-Open is a magnetic tape-based medium used in computer systems for data backup, since it provides large capacities at a low cost, and works differently than common hard drives or solid-state drives, reducing the chance of it failing due to similar reasons.

In 2014, Sony and 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.[2][7]