| 摘要 |
A system can protect data from being stolen or forged. A plurality of data signals not separated by a band-pass filter and including signals of the data within different frequency band and not rewritten even by use of a magnetic card are superimposed, and the resultant signal is recorded in the magnetic recording area of a magnetic card. The system has a reader comprising a band-pass filter, a memory for storing data not rewritten even by use of the above magnetic card, and a subtracting section for subtracting the signal of the data read out of the above memory from the data signal not separated by the above band-pass filter. |
