| 摘要 |
A method of identifying a data carrier (15) such as a credit card, benefit card, access control card, identity card or stored value card, carrying data in the form of a plurality of rational number (12, 13, 14) in a sequence, successive numbers having a marker (11) between them, comprises a) measuring the distance (17) from a fixed point (16) on the data carrier to a given part of a marker, b) dividing this distance by the distance between corresponding given parts of successive markers, thereby obtaining a rational number (x), and c) subtracting this rational number (x) from the number in the sequence adjacent the said marker in a given direction, thereby obtaining a further rational number which is capable of identifying the data carrier uniquely.
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