This tape cartridge was an early example of the 1/4" cartridge (QIC) format of data tape used for long-term storage and backup of computer data. It was invented by 3M in the 1970s and a was departure from the usual tape mechanisms in that it wound a rubber belt around the tape itself to allow for high speed access. Tape cartridges have since increased in density by thousands of times (the tape shown here held 20MB) and are a necessity in any large system. The quarter-inch data cartridge was invented by 3M in the early 70's, and was designed for telecommunications and data acquisition applications calling for the storage of serial data. The tape shown here uses 4 serpentine tracks (accessed by moving the head, not the tape). The quarter-inch cartridge operates with a thin belt that stretches throughout the cartridge mechanism, looping around (and making contact with) both the supply and take-up spools on their outer perimeters. This allows for rapid tape movement.