| 摘要 |
During retrieval of data from tape (10) in a helical scan tape drive mechanism with a rotary head drum (12), movement of tape past the drum by a capstan (15) is controlled to keep the tracks (20,21) recorded on the tape in alignment with paths followed by the heads. A time interval (Int) is measured between occurrence of a drum position pulse generated at a specific angular position of the drum, and detection of reference signals (28a,28b) included in the tracks (such as specific portions, with known bit patterns, of the data in the tracks). The capstan is operated to keep this interval equal to a set reference value, which is recalibrated for example when a new tape is loaded or at a transition between data recordings made at different times. In addition, the timing of window pulses for coordinating operation of read circuitry in the drive is adjusted in accordance with the departure of the recalibrated reference value from a nominal value. <IMAGE>
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