Patent ID: 8577034

Claim:
Method of securing a reading device for card-shaped data carriers to prevent unauthorized evaluation or copying of magnetically encoded data which is detected in the reading device for card-shaped data carriers, whereby a magnetic noise field is generated via a noise field coil disposed in the immediate vicinity of an insertion orifice for inserting card-shaped data carriers or in the region of a legitimate or authorized magnetic field reading head of the reading device in order to disrupt or affect with this noise field a magnetic field reading head which might have been fitted with a view to interception or with fraudulent intent under certain circumstances whilst the magnetic field of a card-shaped data carrier is being recorded, comprising operating or disposing at least one noise field coil so that the authorized magnetic field reading head is also affected by the noise field of the noise field coil as the magnetically encoded data of a card-shaped data carrier is being read, detecting an output or sum signal of the authorized magnetic field reading head generated from the wanted signal of a card-shaped data carrier and from the effects of the noise field, compensating or filtering out the effect of the noise field of the noise field coil in the output or sum signal of the authorized magnetic field reading head or selectively filtering the wanted signals out of the output or sum signal of the authorized magnetic field reading head, evaluating or further processing the wanted signal inside the reading device or in peripheral electronic units, wherein the output signal of the authorized magnetic field reading head corrected with respect to the effect of the noise field is monitored continuously during those phases when no card-shaped data carrier is being inserted in the reading device to ascertain whether a specific total or spectral power is exceeded and, if such is the case, a corresponding status or error message is made available to a primary device controller.