FIELD: information technology.
SUBSTANCE: disclosed is a method of protecting the reading device for data medium in form of a card from unauthorised evaluation or copying of magnetically encoded data which are recorded on the reading device for the data medium in form of a card. A magnetic interference field is generated using an interference field coil. The arrangement of at least one interference field coil is such that an authorised magnetic reading head when reading magnetically encoded data on the data medium in form of a card is also under the effect of the interference field of the interference field coil. An output or resultant signal of the authorised magnetic reading head formed by the useful signal of the data medium in form of a card and the effect of the interference field is detected. The effect of the interference field of the interference field coil on the output or resultant signal of the authorised magnetic reading head is compensated for or filtered, or the useful signal is selectively filtered off from the output or resultant signal of the authorised magnetic reading head.
EFFECT: preventing unauthorised recording of magnetically encoded data on data media in form of a card in the zone of reading devices.
29 cl, 8 dwg
