| 摘要 |
PURPOSE:To prevent the forgery using the heat or contact copy method by laminating a magnetic layer of high coercive force and a magnetic layer of low coercive force on a substrate together with a protecting layer formed on the magnetic layer to obtain a magnetic recording medium and recording the normal signal to the magnetic layer of high coercive force and the dummy signal to the magnetic layer of low coercive force respectively. CONSTITUTION:With use of this magnetic recording medium, the current of a sufficiently high level is made to flow to a magnetic head to magnetize a magnetic layer 12 of high coercive force. Then the dummy signal is recorded to a magnetic layer 13 of low coercive force. In this case, the recording current is sufficient to magnetize the upper layer 13 but not sufficient to magnetize the lower layer 12. Thus the normal recording signal and the dummy signal are superposed on each other. This makes it difficult to copy the normal record by means of the heat or contact copy method. A reading device having three magnetic heads is used to read both normal and dummy signals. That is, the 1st magnetic head 21 reads both normal and dummy signals at a time, the 2nd magnetic head 22 demagnetizes the dummy signal and the 3rd magnetic head 23 reads the normal signal respectively.
|
