| 摘要 |
A credit card includes a non-magnetic substrate and a first strip of permanently magnetic material extending in a first direction along the substrate. The first strip comprises a predetermined series of permanently magnetic lines, the lines defining positions along the first strip and being detectable by a magnetic reader. The predetermined series is disposed on the substrate with at least a pseudo-random starting point. The card also includes a second strip of temporarily magnetizable material extending along the substrate generally parallel to the first strip. The magnetizable material is adapted to have erasable credit indicia imprinted thereon at a spot corresponding to a preselected point in the series of the first strip. Both strips are hidden from view by non-magnetic ink. The system includes elements responsive to the series of lines and gaps of the first strip of each of a number of such cards for imprinting desired credit indicia on the second strip of each card at a spot corresponding to a preselected point in the series of lines and gaps, the location of the spot on the second strip of each card being substantially independent of the location of the spot on the second strips of other such cards. The system also includes elements for reading the second strip of each card and for accepting any indicia found thereon as valid credit indicia only when the preselected position in said series of lines and gaps is detected.
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