| 摘要 |
PURPOSE:To permit the exact change-over of tracks by counting the number of the data blocks processed in a forward direction and the number of the data blocks processed in a backward direction respectively by addition and subtraction on the same data track. CONSTITUTION:A block recognizing circuit 5 detects the data block and an error detecting circuit 4 does not detect an error in the stage of reproducing the data track in the forward direction. Namely, a block counter circuit 7 adds '1' to the number of blocks when the data block is not divided. Said number is not added as the number of blocks with respect to a recognition burst 23 and a burst 24 for automatic gain control. Such process is executed by opening the gate of the circuit 7 when the value counting the tacho pulses from an optical tachometer 13 is above the prescribed value. A zero block detecting circuit 8 which makes subtraction reverse detects the zero of the number of blocks and moves the tape until a marker 21 for detecting the terminal end comes to the position of a read-out head 1.
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