DAT

Sony in the mid 1980’s came up with something called as the DAT or R-DAT which stood for Digital Audio Tapes. DAT Cassettes are a like small audio cassette, made of 4mm DAT magnetic tape that is enclosed in a protective shell and is half the size of a conventional audio cassette.

Dat drives or DAT recorders are closely based on the same principle as that of the video recorder; they have a rotating head and a helical scan assembly through which the data is recorded or read. The standards followed for recording DAT allow only four sampling rates and they are: 32 kHz at 12 bits and 32 kHz, 44.1 kHz or 48 kHz at 16 bits. Dat tapes are about 15 to 180 minutes in length; a standard 120 minute DAT tape would be approximately 60 meters long.

The wide use of DAT happened in the 1990’s in the audio recording industry and even today it comes into use in various scenarios as the archives of the 90’s are still used worldwide. DAT bought along with itself a very important feature of lossless encoding wherein the loss of the data that was to be encoded was minimized to a great extent or one could say that the loss of the data while encoding was as good as nothing. And due to this one could create master tapes using the DAT technology and negate the tape noise (hiss) whilst recording.

DAT machine were very often used by radio broadcasters until recently; even to this date, BBC broadcasting service uses DAT machine as an emergency broadcast which initiates itself in case the player detects a lack of noise for more than the a predetermined time. So in case the studio stopped broadcasting then the DAT would continue the broadcast till the studio could resume its service.

The DAT format was designed primarily for audio usage but then through the ISO Digital Data storage (DDS) standard it was adopted for use as a general purpose data storage medium. It could store from 1.3 GB up to 80 GB on a tape length varying from 60-180 meters depending on the standard and the actual compression level. It is a media which has sequential-access and is used in backup drive which has a DAT recovery function.

The advanced form of DAT tapes that is the DDS tape has 5 versions namely: DDS-1 which stores between 1.3 GB on 60 meters to 2 GB on 90 meters long tape of uncompressed data, DDS-2 provides storing uncompressed 4 GB on 120 meters long tape, DDS-3 (a better version) uses PRML (Partial Response Maximum Likelihood) which is free of electronic noise and stores up to 12 GB of uncompressed data on 125 meter long tape, DDS-4 or also known as DAT 40 stores up to 20 GB on a 150 meter tape length, DAT 72 was developed by HP and Certance and can store up to 36 GB of uncompressed data on a 170 meter long cartridge and is also backwards compatible. Lastly, DAT 160 launched in June 2007 with a slightly different technology of using 8mm wide tapes, compared to the previous versions, almost double the width could store up to 80 GB of uncompressed data with a transfer rate of 6.9 Mb/s.