| 摘要 |
A security document includes a security thread which carries a code, constituted by magnetisable and non- magnetisable portions. The code is a multiple bit code. The position of the thread and its orientation relative to a reading machine can vary within wide limits. The code is read by passing the document under a head which applies a magnetic field to the thread and thereafter the thread is passed under an array 11 of magnetic reading heads which are scanned to provide a repetitive time varying signal representing the code on that part of the thread which has been read. The bits may be read in parallel or sequentially. An array of amplifiers 13 temporarily store the peak voltages derived by the reading heads. A multiplexer 14 sequentially scans the stored signals to derive a time varying signal representative of the binary code. <IMAGE> |
