| 摘要 |
PROBLEM TO BE SOLVED: To easily and surely discriminate a forged magnetic card by detecting a step formed at the boundary of the magnetic material coating surface and the punched hole blocking object of the magnetic card from the dimension of a noise wave at the time of reading magnetic information by means of a magnetic head. SOLUTION: At the time of inserting the magnetic card 1 into an insertion part 2, a flatter component reading circuit 4 measures the change of the dimension of the noise wave, namely the dimension of an S/N, by the roughness of the surface at the magnetic material coating surface 12 of the magnetic card 1. At this time, in the case of a forged card which improves the residual frequency by blocking the punched hole 13 showing a residual frequency with the punched hole blocking object 14 such as silver paper, a punched piece and rewriting magnetic data through the use of a card writer, as the projecting stepped part 15 is formed at the boundary of the magnetic material coating surface 12 and the punched hole blocking object 14 of the magnetic card 1, the noise wave generated by the roughness of the magnetic material surface is grown and namely an abnormally large flutter component is detected. |
