Abbreviation for Rotating Digital Audio Tape as opposed to S-DAT which stands for Stationary Digital Audio Tape technology. R-DAT just refers to what we have all come to know and love simply as DAT. The “R” was originally placed in front of the name because there are some S-DAT systems out there and there needed to be a distinction between the two. R-DAT machines handle tape and record pretty much the same way a modern VCR does (so do ADAT machines for that matter). The tape moves somewhat slowly while the rotating head spins at about 2000 R.P.M. (revolutions per minute) recording the data on the tape in a helical scan fashion, which provides a much higher “effective” tape speed.