2 inch Quadruplex (also called 2″ Quad, or just quad, for short) was the first practical and commercially successful videotape format. It was developed and released for the broadcast television industry in 1956 by Ampex, an American company based in Redwood City, California. This format revolutionized television broadcast operations and production, since the only medium available to the TV industry before then was motion picture film used for kinescopes, which was much more costly to utilize and took more time to develop.
Since most United States West Coast network delays done by the TV networks at the time were done with film kinescopes that needed time for developing, the networks wanted a more practical, cost-effective, and quicker way to time-shift programming for later airing in the West Coast (as well as a general production medium that was not as costly or time-consuming to edit and develop as film). These reasons were part of the motivation for designing a video recording technology that used magnetic tape, in this case, 2 inch Quad.
The format gets its official name of Quadruplex from the fact that it uses 4 heads mounted on a headwheel spinning transversely (width-wise) across the tape at a rate of 14,400 rpm for NTSC-standard Quad decks, and 15,000 rpm for those using the European PAL video standard. This method was called quadrature scanning (as opposed to the helical scan transport used by later videotape formats). The tape ran at a speed of either 7.5 or 15 inches per second (190.5 or 381 mm/s), 15.625 inches per second (396.875 mm/s) PAL, and the audio, control, and cue tracks were recorded in a standard linear fashion near the edges of the tape. The cue track was used either as a second audio track, or for recording cue tones or time code for editing.
