Image Number 4 for United States Patent #5359584.
In recording data on a disk-shaped information recording medium having formed thereon a plurality of concentric or spiral tracks each being divided into a plurality of sectors each having an ID field and a data field, a data mark is selected from a plurality of distinct data marks according to an address of a target sector such that the selected data mark is different from a data mark recorded in an adjacent sector which is contained in an adjacent track. The selected data mark is recorded at the start position of the data field of the target sector. In reproducing the recorded data, a data mark is selected from the plurality of distinct data marks according to an address of a target sector, and is compared with a data mark reproduced from the target sector to detect whether the reproduced data mark coincides with the selected data mark. Sector data in the target sector is reproduced only when the reproduced data mark coincides with the selected data mark.
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