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(DAT) A format for storing music on magnetictape, developed in the mid-1980s by Sony and Philips. Asdigital music was popularized by compact discs, the need fora digital recording format for the consumer existed. Theproblem is that digital music contains over 5 megabytes ofdata per minute before error correction and supplementaryinformation. Before DAT, the only way to record digitally wasto use a video or a reel-to-reel recorder.DAT uses a rotary-head (or "helical scan") format, where theread/write head spins diagonally across the tape like a videocassette recorder. Thus the proper name is "R-DAT", where "R"for rotary distinguishes it from "S-DAT", a stationary designthat did not make it out of the laboratories. Studioreel-to-reel decks are able to use stationary heads becausethey can have wider tape and faster tape speeds, but for thedesired small medium of DAT the rotary-head compromise wasmade despite the potential problems with more moving parts.Most DAT recorders appear to be a cross between a typicalanalog cassette deck and a compact disc player. In additionto the music, one can record subcode information such as thenumber of the track (so one can jump between songs in acertain order) or absolute time (counted from the beginning ofthe tape). The tape speed is much faster than a regular deck(one can rewind 30 minutes of music in 10-25 seconds), thoughnot quite as fast as a compact disc player. DAT decks haveboth analog and digital inputs and outputs.DAT tapes have only one recordable side and can be as long 120minutes.DAT defines the following recording modes with the followingperformance 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 computerDAT recorders use DDS format which is the same as audio DATbut they usually have completely different connectors and itis not always possible to read tapes from one system on theother. Computer tapes can be used in audio machines but areusually more expensive. You can record for two minutes oneach metre of tape.