| 摘要 |
PURPOSE:To achieve the reduction in retrieval time by changing over retrieval speed according to between two sets of non-symmetrical set values in the tracks provided with address numbers and other than between the set values. CONSTITUTION:Two sets of first, second set values are so set in a comparator 2 that the differences from the target track become larger with the first set value non- symmetrically to the target track of the specified address numbers by way of an address assignment part 1. The address number of the track having been read from an address detection system 8 is applied to this comparator 2 and when the number thereof is other than the first, second set values, the head is high speed moved by a feed motor system 4 by way of a control conversion part 3. When the read address number of the detection system 8 becomes between two sets of the set values, the fine retrieval to the terget track in a tracking servo system 5 by the pulses generated in correspondence to the track differences by the pulses generated in correspondence to the address difference through conversion part 3 by the comparing output of the comparator 2 is accomplished, thus the retrieval time is reduced by the combination use of high speed coarse retrieval. |
