| 摘要 |
PURPOSE:To prevent the reading of the data for a vicious user, by recording the noise components or diferent types of data to the data to be recorded at different levels and erasing the noise components or the different data in the reading mode. CONSTITUTION:The noise component N is recorded previously on the genuine data on a magnetic recording layer 1b of a magnetic card MC through a noise generating circuit 9, a DC bias generating circuit 5 and a noise erasing head 4. The card MC is shifted to a position right under a noise erasing head 2, and only the component N is erased. Then the signal corresponding to the genuine data id extracted by a reading head 3. The card MC passed right under the head 3 is shifted to a position right under the head 4 to be superposed on the genuine data again. Thus the component N is recorded. |
