Quarter-inch cartridge
Quarter inch cartridge tape (abbreviated QIC, commonly pronounced "quick") 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 single belt in direct contact with the tape. The tape was originally 1⁄4-inch (6.35 mm) wide and anywhere from 300 to 1,500 feet (91 to 457 m) long. Data is written linearly along the length of the tape in one track (mostly on pre-1980 equipment), or it is serialized and written "serpentine" one track at a time, the drive reversing direction at the end of the tape, each track's data written in the opposite direction to its neighbor. 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 and logical formats. 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 tape 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 tape 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, but the takeup reel is driven by a servo motor or slipping clutch.
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 small beginning or end of tape hole which is detected by an optical sensor, and an "early warning" hole further from each end. 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 and the cartridge will be unusable unless it is reattached.
The design of the QIC tape cartridge is very robust: the aluminium baseplate is an eighth of an inch thick, and the robust plastic cover can withstand abuse and impacts that would damage other tape formats.
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