In a postage meter machine that has a printing unit with a replaceable print head, a print head for such a postage meter machine and a method for the authentication of such a print head, a number of manipulation possibilities are precluded, such as refilling an authorized print head, unauthorized ink...http://www.google.fr/patents/US6406120?utm_source=gb-gplus-shareBrevet US6406120 - Postage meter machine with protected print head
