FIELD: instrumentation.
SUBSTANCE: invention relates to checking of valuable documents with protective elements with several magnetic sections. A valuable document includes at least one high-coercive magnetic section, at least one low-coercive magnetic section and at least one combined magnetic section containing both high-coercive and low-coercive magnetic materials. After magnetisation of all magnetic sections in the first direction the first magnetic signals of the protective element are detected by the first magnetic detector. After the subsequent second magnetisation which is performed in the direction anti-parallel to the direction of the first magnetisation, and remagnetising only low-coercive magnetic material the second magnetic signals of the protective element are detected. For identification of magnetic sections the second magnetic signals or their derivative signal is compared with two threshold levels.
EFFECT: improved reliability of detection of magnetic sections.
17 cl, 7 dwg
