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 discs, 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)