Digital audio tape
Digital Audio Tape (DAT or R-DAT) is a signal recording and playback medium introduced by Sony in 1987. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As the name suggests the recording is digital rather than analog, DAT converting and recording at higher equal or lower sampling rates than a CD (48, 44.1 or 32 kHz sampling rate, and 16 bits quantization) without data compression. This means that the entire input signal is retained. If a digital source is copied then the DAT will produce an exact clone, unlike other digital media such as Digital Compact Cassette or MiniDisc, both of which use lossy data compression. The technology of DAT is closely based on that of video recorders, using a rotating head and helical scan to record data. This, crucially or not, prevents DATs from being physically edited.