摘要 |
A method of testing a security having a mechanically testable identifying mark, for example a security thread, which has a physical property, for example electric conductivity, which can be measured without contact by means of a first field, for example, an electric field. The physical property can be reproducibly influenced by the effect of a second field, for example an electromagnetic field. If this influence takes place periodically, a signal is produced as a measured variable modulated according to the mutual effect of the two fields.
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