资料来源 : Free On-Line Dictionary of Computing

Digital Audio Tape
     
         (DAT) A format for storing music on magnetic
        tape, developed in the mid-1980s by {Sony} and {Philips}.  As
        digital music was popularized by {compact disc}s, the need for
        a digital recording format for the consumer existed.  The
        problem is that digital music contains over 5 megabytes of
        data per minute before error correction and supplementary
        information.  Before DAT, the only way to record digitally was
        to use a video or a reel-to-reel recorder.
     
        DAT uses a rotary-head (or "helical scan") format, where the
        read/write head spins diagonally across the tape like a video
        cassette recorder.  Thus the proper name is "R-DAT", where "R"
        for rotary distinguishes it from "S-DAT", a stationary design
        that did not make it out of the laboratories.  Studio
        reel-to-reel decks are able to use stationary heads because
        they can have wider tape and faster tape speeds, but for the
        desired small medium of DAT the rotary-head compromise was
        made despite the potential problems with more moving parts.
     
        Most DAT recorders appear to be a cross between a typical
        analog cassette deck and a {compact disc} player.  In addition
        to the music, one can record subcode information such as the
        number of the track (so one can jump between songs in a
        certain order) or absolute time (counted from the beginning of
        the tape).  The tape speed is much faster than a regular deck
        (one can rewind 30 minutes of music in 10-25 seconds), though
        not quite as fast as a compact disc player.  DAT decks have
        both analog and digital inputs and outputs.
     
        DAT tapes have only one recordable side and can be as long 120
        minutes.
     
        DAT defines the following recording modes with the following
        performance specifications...
     
           2 channel 48KHz Sample rate, 16-bit linear encoding
           120 min max.
           Frequency Response 2-22KHz (+-0.5dB)
           SN = 93 dB   DR = 93 dB
     
           2 channel 44.1Khz Sample rate, 16-bit linear encoding
           120 min max
           Frequency Response 2-22KHz (+-0.5dB)
           SN = 93 dB   DR = 93 dB
     
           2 channel 32KHz Sample Rate, 12-bit non-linear encoding
           240 min max
           Frequency Response 2-14.5KHz (+-0.5dB)
           SN = 92 dB   DR = 92 dB
     
           4 channel 32KHz (not supported by any deck)
     
        DAT is also used for recording computer data.  Most computer
        DAT recorders use DDS format which is the same as audio DAT
        but they usually have completely different connectors and it
        is not always possible to read tapes from one system on the
        other.  Computer tapes can be used in audio machines but are
        usually more expensive.  You can record for two minutes on
        each metre of tape.
     
        (1995-02-09)