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Technology: Midget machine puts recording on a new track

作者:勾徉坪    发布时间:2019-02-28 07:04:12    

IN THE guise of a humble dictation machine, Sony will soon launch a digital tape recorder which is fundamentally different from any existing technology. The new recorder relies on electronics rather than precision mechanics to play back the digital code recorded on the tape. Sony developed the system for use in a small dictation machine, which will go on sale at the end of this year. The pocket machine can record two hours of digital mono sound with the quality of FM radio. The cassette is the size of a large postage stamp. If it is successful, Sony could in future apply the technology to other types of digital recorder – for computer data, hi-fi stereos and even videos. In a conventional digital audio tape recorder, tiny recording heads on a rapidly rotating drum scan the tape obliquely to lay down parallel, helical tracks, like the threads of a screw. Each track is less than 14 micrometres wide, a quarter of the width of a human hair. To play back, an electronic servo system steers the heads over the track pattern to an accuracy of micrometres. The servo must compensate for changes in the tape caused by stretching or variations in temperature, and for errors when dif ferent machines are used for recording and playback. The new system records helical tracks in much the same way, but divides the digital data into numbered blocks. To play back, no attempt is made to follow the tracks accurately. The heads move at twice the speed used for recording and sweep over the general area of the tracks, reading at least four at a time. So the same data can be read four times over. All the data read are stored in memory chips, where they are reassembled in the correct order and the redundant blocks discarded. Relieving the heads of the burden of accurate tracking means that the mechanism can be much simpler. Instead of lacing the tape round the drum, as in a video recorder, the new system simply moves the drum into the cassette and against the tape,

 

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