The present invention relates to a pen for sensing coded data on a page. The coded data is printed on the page as a collection of tags using invisible ink. The pen includes an elongate housing defining an internal space. An ink marking implement is movably mounted within the space and includes an ink...http://www.google.fr/patents/US7663775?utm_source=gb-gplus-shareBrevet US7663775 - Wireless transmitter pen
