D/CAS (Data/CASsette), also known as a streamer cassette, is a now-obsolete data backup technology that uses an upgraded version of the common audio tape cassette. It can hold anywhere from 200 to 600 megabytes of data. It uses a specialized tape drive based from a audio cassette transport. It was superseded by newer data tape storage formats such as Travan, QIC, DDS, and LTO.
Streamer cassettes look almost like a standard audio cassette, with the addition of having a notch about one quarter-inch wide and deep situated slightly off-center at the top edge of the cassette. They also have a reusable write-protect tab on only one side of the top edge of the cassette, with the other side of the top edge having either only an open rectangular hole, or no hole at all. This is due to a streamer cassette being basically one-sided, due to the entire one-eighth inch width of the tape and its 4 tracks (much like an audio cassette) recorded all across said width being used all at once by a streamer cassette drive for the writing and reading of data. The 4 tracks are sequentially written to in a serpentine fashion, as opposed to audio cassettes splitting up half of the 4 tracks for each of its 2 sides, hence streamer cassettes being "single-sided". The multi-track serpentine layout of a D/CAS/streamer cassette is very much like the track layout of the aforementioned newer data tape formats like QIC and Travan.
Streamer cassettes can be inserted and used in an audio cassette deck, but the formulation of tape loaded in them is suited and optimized only for full saturation-level square-wave-pulsed digital data recording and playback, resulting in traditional analog audio recordings made on them having very poor audio quality with a large amount of noise and distortion upon playback.
- "YourDictionary D/CAS definition". Your Dictionary (yourdictionary.com). Retrieved 5 December 2013.
- "TEAC D/CAS cassettes catalogue". Pacific Data (pacificdatastorage.com). Retrieved 5 December 2013.
- "Tape backup explanation". ThinkQuest (thinkquest.org). Archived from the original on 29 June 2012. Retrieved 5 December 2013.
- Museum of Obsolete Media's page on streamer cassettes
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