1.
Magnetic tape data storage
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Magnetic tape data storage is a system for storing digital information on magnetic tape using digital recording. Modern magnetic tape is most commonly packaged in cartridges and cassettes, the device that performs writing or reading of data is a tape drive. Autoloaders and tape libraries automate cartridge handling, for example, a common cassette-based format is Linear Tape-Open, which comes in a variety of densities and is manufactured by several companies. Sony announced in 2014 that they had developed a storage technology with the highest reported magnetic tape data density,148 Gbit/in². Initially, magnetic tape for storage was wound on 10. 5-inch reels. This de facto standard for computer systems persisted through the late 1980s. Tape cartridges and cassettes were available as early as the mid-1970s and were used with small computer systems. With the introduction of the IBM3480 cartridge in 1984, large computer systems started to move away from open reel tapes, magnetic tape was first used to record computer data in 1951 on the Eckert-Mauchly UNIVAC I. The UNISERVO drive recording medium was a metal strip of 0. 5-inch wide nickel-plated phosphor bronze. Recording density was 128 characters per inch on eight tracks at a speed of 100 in/s. Of the eight tracks, six were data, one was a parity track, making allowance for the empty space between tape blocks, the actual transfer rate was around 7,200 characters per second. A small reel of mylar tape provided separation from the metal tape, IBM computers from the 1950s used ferrous-oxide coated tape similar to that used in audio recording. IBMs technology soon became the de facto industry standard, magnetic tape dimensions were 0. 5-inch wide and wound on removable reels up to 10.5 inches in diameter. Different tape lengths were available with 1,200 feet and 2,400 feet on mil, during the 1980s, longer tape lengths such as 3,600 feet became available using a much thinner PET film. Most tape drives could support a maximum size of 10.5 inches. CDC used IBM compatible 1/2 inch magnetic tapes, but also offered a 1 inch wide variant, a so-called mini-reel was common for smaller data sets, such as for software distribution. These were 7-inch reels, often with no fixed length—the tape was sized to fit the amount of data recorded on it as a cost-saving measure. Early IBM tape drives, such as the IBM727 and IBM729, were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long u-shaped loops of tape
2.
Sony
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Sony Corporation is a Japanese multinational conglomerate corporation that is headquartered in Kōnan, Minato, Tokyo. Its diversified business includes consumer and professional electronics, gaming, entertainment, the company is one of the leading manufacturers of electronic products for the consumer and professional markets. Sony was ranked 116th on the 2015 list of Fortune Global 500 and these make Sony one of the most comprehensive entertainment companies in the world. The group consists of Sony Corporation, Sony Pictures Entertainment, Sony Interactive Entertainment, Sony Music Entertainment, Sony Financial Holdings and others. Sony is among the Semiconductor sales leaders by year and as of 2013, the companys current slogan is BE MOVED. Their former slogans were make. believe, like. no. other, Sony has a weak tie to the SMFG keiretsu, the successor to the Mitsui keiretsu. Sony began in the wake of World War II, in 1946, Masaru Ibuka started an electronics shop in a department store building in Tokyo. The company had $530 in capital and a total of eight employees, in the following year he was joined by his colleague, Akio Morita, and they founded a company called Tokyo Tsushin Kogyo 東京通信工業. The company built Japans first tape recorder, called the Type-G, in 1958 the company changed its name to Sony. When Tokyo Tsushin Kogyo was looking for a name to use to market themselves, they strongly considered using their initials. The primary reason they did not is that the railway company Tokyo Kyuko was known as TTK, the company occasionally used the acronym Totsuko in Japan, but during his visit to the United States, Morita discovered that Americans had trouble pronouncing that name. Another early name that was tried out for a while was Tokyo Teletech until Akio Morita discovered that there was an American company already using Teletech as a brand name, the name Sony was chosen for the brand as a mix of two words. One was the Latin word sonus, which is the root of sonic and sound, and the other was sonny, a common slang term used in 1950s America to call a boy. In the 1950s Japan sonny boys, was a word into Japanese which connoted smart and presentable young men. The first Sony-branded product, the TR-55 transistor radio, appeared in 1955, at the time of the change, it was extremely unusual for a Japanese company to use Roman letters to spell its name instead of writing it in kanji. The move was not without opposition, TTKs principal bank at the time and they pushed for a name such as Sony Electronic Industries, or Sony Teletech. Akio Morita was firm, however, as he did not want the company tied to any particular industry. Eventually, both Ibuka and Mitsui Banks chairman gave their approval, according to Schiffer, Sonys TR-63 radio cracked open the U. S. market and launched the new industry of consumer microelectronics
3.
Linear Tape-Open
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Hewlett Packard Enterprise, IBM and Quantum control the LTO Consortium, which directs development and manages licensing and certification of media and mechanism manufacturers. The standard form-factor of LTO technology goes by the name Ultrium, the seventh generation of LTO Ultrium was released in 2015 and can hold 6.0 TB in a cartridge of the same size. Upon introduction, LTO Ultrium rapidly defined the super tape market segment and has consistently been the best-selling super tape format, LTO is widely used with small and large computer systems, especially for backup. Half-inch magnetic tape has been used for storage for more than 60 years. In the mid 1980s, IBM and DEC put this kind of tape into a single reel, although the physical tape was nominally the same size, the technologies and intended markets were significantly different and there was no compatibility between them. IBM called its format 3480 and designed it to meet the requirements of its mainframe products. DEC originally called theirs CompacTape, but later it was renamed DLT, in the late 1980s, Exabytes Data8 format, derived from Sonys dual-reel cartridge 8 mm video format, saw some popularity, especially with UNIX systems. Sony followed this success with their own now-discontinued 8 mm data format, by the late 1990s, Quantums DLT and Sonys AIT were the leading options for high-capacity tape storage for PC servers and UNIX systems. These technologies were tightly controlled by their owners, consequently, there was little competition between vendors and the prices were relatively high. To counter this, IBM, HP and Seagate formed the LTO Consortium, much of the technology is an extension of the work done by IBM at its Tucson lab during the previous 20 years. Around the time of the release of LTO-1, Seagates magnetic tape division was spun off as Seagate Removable Storage Solutions, later renamed Certance, despite the initial plans for two form-factors of LTO technology, only Ultrium was ever produced. In common usage, LTO generally refers to the Ultrium form factor, as of 2015, seven generations of LTO Ultrium technology have been made available and three more are planned. Between generations, there are strict compatibility rules that describe how, notes Data capacity and speed figures above are for uncompressed data. Most manufacturers list compressed capacities on their marketing material, capacities are often stated on tapes as double the actual value, they assume that data will be compressed with a 2,1 ratio. See Compression below and the table above, the units for data capacity and data transfer rates generally follow the decimal SI prefix convention and not the binary prefix convention. Minimum and maximum reading and writing speeds are drive-dependent, in contrast to other tape technologies, an Ultrium cartridge is rigidly defined by a particular generation of LTO technology and cannot be used in any other way. While Ultrium drives are also defined by a generation, they are required to have some level of compatibility with older generations of cartridges. The rules for compatibility between generations of drives and cartridges is as follows, An Ultrium drive can read data from a cartridge in its own generation and the two prior generations
4.
VXA
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VXA is a tape backup format originally created by Ecrix and now owned by Tandberg Data. After the merger between Ecrix and Exabyte, VXA was produced by Exabyte Corporation, on November 20,2006, Exabyte was purchased by Tandberg Data who has since stopped further development of the format. Exabyte and Ecrix describe the format as packet technology. Since VXA is based on helical scan technology, data is written across the tape from side to side in helical strips, the novel part of VXA packet technology is that each stripe starts with a unique packet ID and ends with an ECC packet checksum. As each stripe is written to tape, it is read back to verify that the write was successful. If the write was not 100% successful the packet can be rewritten at another point on the tape without stopping, when the data is read back, the packets are reassembled into a buffer by their packet ID. The buffer has 3 additional ECCs to ensure data integrity, another aspect of VXA is that there are 2 read heads for each stripe, slightly offset in relation to each other to allow for more flexibility in reading tapes written by other drives. Due to the relatively slow tape speed inherent to helical scan technology, the VXA format competes mainly against the DDS, and DLT-IV formats. Exabyte released two different product lines based on VXA-3 technology, VXA-320 in 2005 and VXA-172 in 2006, VXA-172 drives are limited to 86 GB per tape cartridge, but can be unlocked to remove the limit. VXA-3 was the first helical scan system in production to feature thin film MR heads, Data Capacity figures above are for uncompressed data. Exabyte assumes a 2x compression factor in their marketing material, ECMA222 Specification of ALDC, the data compression standard for VXA-1
5.
8 mm video format
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The 8mm video format refers informally to three related videocassette formats for the NTSC and PAL/SECAM television systems. These are the original Video8 format and its improved successor Hi8 and their user base consisted mainly of amateur camcorder users, although they also saw important use in the professional television production field. In 1985, Sony of Japan introduced the Handycam, one of the first Video8 cameras with commercial success, much smaller than the competitions VHS and Betamax video cameras, Video8 became very popular in the consumer camcorder market. The three formats are very similar, featuring both the same magnetic tape width and near-identical cassette shells, measuring 95 ×62.5 ×15 mm. This gives a measure of compatibility in some cases. One difference between them is in the quality of the tape itself, but the differences lie in the encoding of the video when it is recorded onto the tape. Video8 was the earliest of the three formats, and is entirely analog and it was followed by Hi8, a version with improved resolution. Although this was still analog, some professional Hi8 equipment could store additional digital stereo PCM sound on a reserved track. Digital8 is the most recent 8mm video format and it retains the same physical cassette shell as its predecessors, and can even record onto Video8 or Hi8 cassettes. However, the format in which video is encoded and stored on the tape itself is the entirely digital DV format, some Digital8 camcorders support Video8 and Hi8 with analog sound, but this is not required by the Digital8 specification. In all three cases, a length of 8mm-wide magnetic tape is wound between two spools and contained within a hard-shell cassette and these cassettes share similar size and appearance with the audio cassette, but their mechanical operation is far closer to that of VHS or Betamax videocassettes. Standard recording time is up to 180 minutes for PAL and 120 minutes for NTSC, like most other videocassette systems, Video8 uses a helical-scan 40mm head drum to read from and write to the magnetic tape. The drum rotates at high speed while the tape is pulled along the drums path, because the tape and drum are oriented at a slight angular offset, the recording tracks are laid down as parallel diagonal stripes on the tape. Unlike preceding systems, 8mm did not use a track on the tape to facilitate the head following the diagonal tracks. Instead 8mm recorded a sequence of four sine waves on each video track such that adjacent tracks would produce one of two heterodyne frequencies if the head mistracked, the system automatically adjusted the tracking such that the two frequencies produced were of equal magnitude. This system was derived from the track following used by the Philips Video 2000 system. Sony rechristened the system as automatic track following as the 8mm system lacked the ability of the heads to physically move within the head drum. The main disadvantage of the ATF system was that unlike in the case of a control track and this made editing using a non linear editing system problematic
6.
Hewlett-Packard
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The Hewlett-Packard Company or shortened to Hewlett-Packard was an American multinational information technology company headquartered in Palo Alto, California. The company was founded in a garage in Palo Alto by William Bill Redington Hewlett and David Dave Packard. HP was the worlds leading PC manufacturer from 2007 to Q22013 and it specialized in developing and manufacturing computing, data storage, and networking hardware, designing software and delivering services. HP also had services and consulting business around its products and partner products.4 billion in 2008, in November 2009, HP announced the acquisition of 3Com, with the deal closing on April 12,2010. On April 28,2010, HP announced the buyout of Palm, on September 2,2010, HP won its bidding war for 3PAR with a $33 a share offer, which Dell declined to match. On October 6,2014, Hewlett-Packard announced plans to split the PC and printers business from its enterprise products, the split closed on November 1,2015, and resulted in two publicly traded companies, HP Inc. and Hewlett Packard Enterprise. William Redington Hewlett and David Packard graduated with degrees in engineering from Stanford University in 1935. The company originated in a garage in nearby Palo Alto during a fellowship they had with a past professor, Terman was considered a mentor to them in forming Hewlett-Packard. In 1939, Packard and Hewlett established Hewlett-Packard in Packards garage with a capital investment of US$538. Hewlett and Packard tossed a coin to decide whether the company they founded would be called Hewlett-Packard or Packard-Hewlett, HP incorporated on August 18,1947, and went public on November 6,1957. Of the many projects they worked on, their very first financially successful product was an audio oscillator. This allowed them to sell the Model 200A for $54.40 when competitors were selling less stable oscillators for over $200, the Model 200 series of generators continued until at least 1972 as the 200AB, still tube-based but improved in design through the years. They worked on technology and artillery shell fuses during World War II. Hewlett-Packards HP Associates division, established around 1960, developed semiconductor devices primarily for internal use, instruments and calculators were some of the products using these devices. HP partnered in the 1960s with Sony and the Yokogawa Electric companies in Japan to develop several high-quality products, the products were not a huge success, as there were high costs in building HP-looking products in Japan. HP and Yokogawa formed a joint venture in 1963 to market HP products in Japan, HP bought Yokogawa Electrics share of Hewlett-Packard Japan in 1999. HP spun off a company, Dynac, to specialize in digital equipment. The name was picked so that the HP logo hp could be turned upside down to be a reverse image of the logo dy of the new company
7.
DECtape
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DECtape was a magnetic tape data storage medium used with many Digital Equipment Corporation computers, including the PDP-6, PDP-8, LINC-8, PDP-9, PDP-10, PDP-11, PDP-12, and the PDP-15. On DECs 32-bit systems, VAX/VMS support for it was implemented, DECtapes were 3/4 inch wide, and formatted into blocks of data that could each be read or written individually. Each tape stored 184K 12-bit PDP-8 words or 144K 18-bit words, block size was 128 12-bit words, or 256 18-bit words for the other machines. From a programming point of view, DECtape behaved like a very slow disk drive, DECtape had its origin in the LINCtape tape system, which was originally designed by Wesley Clark at the MIT Lincoln Laboratory as an integral part of the LINC computer. There were simple LINC instructions for reading and writing tape blocks using a machine instruction. The design of the LINC, including LINCtape, was placed in the domain because its development had been funded by the government. LINCtape drives were manufactured by companies, including Digital. In turn, LINCtapes origin can be found in the magnetic tape system for the historic Lincoln Laboratory TX-2 computer, designed by Richard L. The TX-2 Tape System is the ancestor of LINCtape, including the use of two redundant sets of five tracks and a direct drive tape transport, but it used a physically incompatible tape format. Digital initially introduced the Type 550 Microtape Control and Type 555 Dual Microtape Transport as peripherals for the PDP-1 and PDP-4 computers, the initial specifications for the Type 550 controller discussed a significant advance beyond the LINCtape, the ability to read and write in either direction. By late 1964, the Type 555 transport was being marketed as a DECtape transport, the tape transport used on the LINC was essentially the same as the Type 555 transport, with the same interface signals and the same physical tape medium. The LINC and DEC controllers, however, were incompatible, while LINCtape supported high-speed bidirectional block search, it only supported actual data read and write operations in the forward direction. DECtape used a different mark track format to provide for the possibility of read and write operations in either direction. DEC applied for a patent on the features incorporated into DECtape in late 1964. It is notable that the inventor listed on this patent, Thomas Stockebrand, was also an author of the paper on the TX-2 tape system from which the LINC tape was derived. Eventually, the TC12-F tape controller on the PDP-12 supported both LINCtape and DECtape on the same transport, as with the earlier LINC-8, the PDP-12 was a PDP-8 augmented with hardware support for the LINC instruction set and associated laboratory peripherals. DECtape was designed to be reliable and durable enough to be used as the storage medium for a computers operating system. It was possible, although slow, to use a DECtape drive to run a small OS such as OS/8 or OS/12
8.
Commodore Datasette
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The Commodore 1530 Datasette was Commodores dedicated magnetic tape data storage device. Using compact cassettes as the medium, it provided inexpensive storage to Commodores 8-bit home/personal computers, notably the PET, VIC-20. A physically similar model, Commodore 1531, was made for the Commodore 16, unlike most microcomputer storage methods using compact cassettes, the Datasette uses a digital format. Instead of writing two tones to tape to indicate bits, patterns of waves are used including a parity bit. Programs are written twice to tape for error correction, if an error is detected when reading the first recording, the Datasette has built-in analog to digital converters and audio filters to convert the computers digital data into analog sound and vice versa. Connection to the computer is done via an edge connector or mini-DIN connector. The Datasette was more popular outside than inside the United States, in the United States disk drives quickly became standard, despite the Commodore 1541 floppy drive costing roughly five times as much as a Datasette. In most parts of Europe, the Datasette was the medium of choice for years after its launch. The inexpensive and widely available audio cassettes made the Datasette a good choice for the home computer mass market. The Datasette is slow—but because of its digital format extremely reliable—transferring data at around 50 bytes per second, after the Datasettes launch, however, special turbo tape software appeared, providing much faster tape operation. Such software was integrated into most commercial prerecorded applications, as well as being available separately for loading and saving the users homemade programs and these programs were only widely used in Europe, as the US market had long since moved onto disks. Datasettes can typically store about 100 kByte per 30 minute side, the use of turbo tape and other fast loaders increased this number to roughly 1000 kByte. The Datasette has only one cable with a PCB edge connector at the computer end. All input/output signals to the datasette are all digital and so all digital to analog, power is also included in this cable. The pinout is ground, +5 V DC, motor, read, write, the sense signal monitors the play, rewind, and fast-forward buttons, but cannot differentiate between them. A mechanical interlock prevented any two of them being pressed at the same time, unregulated 6.36 V DC is used to power the cassette motor. To record physical data, the zero-crossing from positive to negative voltage of the signal is measured. The resulting time between these positive to negative crossings is then compared to a threshold to determine whether the time since the last crossing is short or long, note the lower amplitude for the shorter periods
9.
Helical scan
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Helical scan is a method of recording high frequency signals on magnetic tape. It is used in video tape recorders, video cassette recorders, digital audio tape recorders. In a fixed tape head recording system, magnetic tape is drawn past the head at a constant speed. The head creates a magnetic field in response to the signal to be recorded. As the tape moves away, the magnetic particles carry an imprint of the signal in their magnetic orientation. If the tape moves too slowly, a frequency signal will not be imprinted. Thus the bandwidth capacity of the recorded signal can be seen to be related to tape speed, the faster the speed. Digital video and digital audio need considerably more bandwidth than analog audio and this is impractical, since tapes of immense length would be required. The generally adopted solution is to rotate the head against the tape at high speed, so that the velocity is high. To accomplish this, the head must be tilted so that at each rotation of the head, each segment of the signal is recorded as a diagonal stripe across the tape. This is known as a helical scan because the tape wraps around the drum at an angle. The difference between the writing speed and linear tape speed is vast, for example,13 mph versus 35 mm/s. The helical scan method of recording was first developed by Eduard Schüller, with the advent of television broadcasting in Japan in the early 1950s, they saw the need for magnetic television signal recording just as engineers in the United States and Europe did. Thus, when tape motion was stopped, only a segment of the picture recording was present at the playback heads. The motivation to overcome this limitation led, in part, to the development of the helical scan system, toshiba introduced helical scan technology to the television industry in 1959. During the 1960s and 1970s, helical scan recording machines were introduced by many manufacturers and these factors also made it possible eventually to bring video recording to users at home, in a cassette format. There were a number of problems to be overcome with this system, the high tape/head speed could lead to rapid wear of both the tape and the head, so both need to be highly polished, and the head made of a hard, wear resistant material. Most systems operate with an air bearing separating the heads from the surface of the drum, supplying signals to a rotating head is also problematic, This is usually accomplished by coupling the signal inductively through a rotary transformer
10.
9 track tape
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The IBM System/360, released in 1964, introduced what is now generally known as 9 track tape. Data is stored as 8-bit characters, spanning the width of the tape. Various recording methods were employed during its lifetime as tape speed and data density increased, including PE, GCR, tapes came in various sizes up to 3,600 feet in length. The standard size of a byte was effectively set at eight bits with the S/360, the control electronics would then indicate to the controlling computer that the unit was ready for operation. Like its audio counterpart, moving tape past the heads on nine-track digital required precise control. The capstan motor was designed for smooth operation. Feedback to the electronics was accomplished by a tachometer, usually an optical tone wheel. Starting and stopping the capstan was controlled by ramp generators to ensure a properly sized inter-record gap, the vacuum columns were chambers open at one end, the openings being in line with the tape path before and after the capstan and roller assemblies. The amount of tape in the column was controlled by four optical or vacuum sensors on the sides of the columns. The control electronics kept the curve of the loop between the two inner sensors, cueing the supply reel to feed more or the take-up reel to take more as necessary. Tape motion on many systems was bidirectional, i. e. tape could be either forward or backward at the request of the controlling computer. Because the supply vacuum column kept a small, constant tension in the reverse direction, unlike most audio tape systems, the capstan and head assemblies were always in contact with the tape, even during fast forward and rewind operations. Tapes included an end-of-tape foil strip, when EOT was encountered while writing, the computer program would be notified of the condition. This gave the program a chance to write information on the tape while there was still enough tape to do so. The sensing of BOT and EOT was achieved by shining a small lamp at the surface at an oblique angle. When the foil strip moved past the lamp a photo-receptor would see the flash of light. This is the reason that photographic flash cameras were not allowed in data centers since they could trick the tape drives into falsely sensing BOT and EOT. The above describes a typical system, however, manufacturers engineered many alternative designs
11.
Quarter-inch cartridge
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Quarter inch cartridge tape is a magnetic tape data storage format introduced by 3M in 1972, with derivatives still in use as of 2016. QIC comes in a rugged enclosed package of aluminum and plastic that holds two tape reels driven by a belt in direct contact with the tape. The tape was originally 1⁄4-inch wide and anywhere from 300 to 1,500 feet long, since the introduction of QIC, it has been widely used and many variations exist. There is a QIC trade association that publishes QIC standards which include interfaces, to a very large extent it was the efficiency and openness of this organization which encouraged hardware and software developers to use this type of drive and media. The QIC cartridge is distinguished from other types of cartridges by the fact that it contains an endless drive belt which is moved at a uniform speed by a motorised capstan. Since the belt is in contact with the tape, this ensures both that the moves at uniform speed, and that neutral tension is maintained at all times. This is in contrast to cassette tapes or DATs where the tape is moved past the head by a capstan and pinch wheel, the tape in a QIC cartridge is not physically attached to the reels and is never completely unwound. This is again different from other cassettes or cartridges, which generally have some form of clip anchoring on at least one end of the tape. To ensure that the tape is never completely unwound, each end has a beginning or end of tape hole which is detected by an optical sensor. If a defective drive—for example with fluff in a sensor—winds the tape past the BOT or EOT marker, the tape will detach from the spool, however, because the tape is belt-driven, seeking back and forth can eventually cause the tape to become unevenly tensioned. It is therefore necessary to periodically retension the cartridge and this is accomplished by winding the tape from beginning to end and back in one operation, allowing the belt to equalize itself. For newer QIC drives that use a SCSI interface, there is a SCSI RETENSION command to do this, when the cartridge gets old, the belt may not provide enough friction to turn the takeup spool smoothly. When this happens, the tape will need to be replaced, in some cases a cartridge must be formatted before use. The capability to do this is in the rather than the host computer. The first QIC tape format was the 5.875 in by 3.875 in Data Cartridge format with two internal belt-driven reels and a metal base. The original product, the DC300, has 300 feet of tape and holds 200 kilobytes. 35GB on a DC9135 cartridge Other QIC DC standards include the QIC-02, later QIC DC drives usually use the SCSI interface. Later, the smaller Minicartridge form-factor was introduced and this is 2.375 in by 3.125 in size and is small enough to fit in a 3.5 in drive bay. Travan is an evolution of the QIC Minicartridge format, sold for computer use
12.
IBM 7 track
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IBMs first magnetic tape data storage devices, introduced in 1952, use what is now generally known as 7 track tape. The magnetic tape is 1/2 wide and there are six tracks plus one parity track for a total of seven parallel tracks that span the length of the tape. Data is stored as six-bit characters, with bit of the character. These tape drives were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long U-shaped loops of tape, between active control of powerful reel motors and vacuum control of these U-shaped tape loops, extremely rapid start and stop of the tape at the tape-to-head interface could be achieved. When active, the two tape reels thus fed tape into or pulled out of the vacuum columns, intermittently spinning in rapid. Stock shots of such vacuum-column tape drives in motion were used to represent the computer in films. Density Initial recording density was 100 characters per inch, later models supported 200,556 and 800 characters per inch. Inter-record Gap A gap between records allowed the time to start and stop the tape. Latency There was only a 1. 5ms delay for the tape to reach its full reading or writing speed. Markers Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning, write protection A removable plastic ring in the back of the tape reel was inserted to indicate writing should be permitted. The IBM726 dual magnetic tape reader/recorder for the IBM701 was announced on May 21,1952, the IBM727 Magnetic Tape Unit was announced for the IBM701 and IBM702 on September 25,1953. It became IBMs standard tape drive for their vacuum tube era computer systems and it was withdrawn on May 12,1971. The IBM728 magnetic tape drive was used on the SAGE AN/FSQ-7 computer and it was physically similar to the IBM727, but with significantly different specifications. Tracks,6 Data,1 synchronization words,6 chars words/inch,41.33 The IBM729 Magnetic Tape Unit was IBMs iconic tape mass storage system from the late 1950s through the mid-1960s and it was used on late 700, most 7000 and many 1400 series computers. A new dual gap head assembly allowed read-after-write verification, the IBM7330 Magnetic Tape Unit was a low cost slower tape system. It was common on 1400 series computers, the 2400 Series Magnetic Tape Units were introduced with the System/360. Most were IBM9 Track format drives, but they could be ordered with seven-track read/write heads, allowing them to read and write seven-track tapes
