Lgz Landis Gyr Zug Ag

Andrzej Niepolomski

David L Greenaway

The present invention is a method and apparatus for validating a valuable document such as a debit card. The valuable document includes a plurality of value markings arranged to form a code word. Illustratively, the value markings may be optical elements capable diffracting incident optical radiation. Alternatively, the value marking may be electrical elements such as safety fuses, diodes or transistors, the presence or absence of the electrical element representing a logic '1' or logic '0' respectively. In accordance with the present invention, the code word is first read to determine if it is valid. If the code word is valid, one or more value markings are erased, in each of plurality of erasing steps, until, illustratively after the final erasing step all of the value markings are erased. After each erasing step, the erased and remaining unerased validations markings form a new code word. If the sequence of new code words corresponds to a predetermined sequence of code words a signal is produced. Illustratively, the signal corresponds to a cash value represented by the predetermined sequence of code words.

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Baar, Switzerland

Andrzej Niepolomski