The invention is directed to an X-Y co-ordinate detection system of the type which generates intersecting paths of radiation across a surface which may be, for example, a touch panel of the cathode ray tube type. Less expensive and more reliable operation is provided by developing the paths of radiation...http://www.google.fr/patents/US4459476?utm_source=gb-gplus-shareBrevet US4459476 - Co-ordinate detection system
