A transmitter pen positioning system is provided, in which a pen, having multiple output elements, is used to accurately determine the location of the pointing tip of the pen, in relation to the writing area of a surface, such as a white board. The first output element, preferably an infrared transducer,...http://www.google.fr/patents/US20010000666?utm_source=gb-gplus-shareBrevet US20010000666 - Transmitter pen location system
