| 摘要 |
A card is provided which includes a homogeneous sheet of magnetic material. The material and thickness of the magnetic sheet are such that portions may be permanently magnetized in a direction transverse to the plane of the sheet and with a polarity which cannot be disturbed except by directing magnetic flux in the opposite direction through the sheet. A plurality of such portions are permanently magnetized to provide a card with a plurality of magnetic poles at one face of one polarity or the other and distributed to code the card. In addition, a further irregular or random magnetizing pattern is imparted to the sheet, whereby the card magnetization is effectively scrambled to render the code undecipherable and unintelligible. |
