Graphics table particularly for a telewriting system
OwnerJean-Claude Rahuel, Jean-Paul Dagnelieinventors
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Abstract
A graphics table comprises a non-conductive plate supporting two crossing layers of wires and a pen for writing on a sheet disposed on the plate. The wires are successively scanned by an electric current which creates a field to be detected by the pen. The electric current has a high frequency, for example of the order of ten megahertz, and the wires are switched at a frequency of for example one hundred kilohertz. The pen is followed by a selective amplifier of ten megahertz, by a filter, by a detector, and by a circuit for determining the time when the picked up signal passes through a peak. The invention is notably useful in a telewriting system.
Claims4
A graphics table comprising a non-conductive plate means carrying two orthogonally oriented sets of wires and a coaxial pen means capable of picking up electrical signals and of writing on a sheet of paper placed on the non-conducting plate, means for successively scanning the wires of one set and of the other by an electric current, and said pen comprising reception means for a field created by the electric current successively applied to the wires during the scanning of the sets of wires, characterized in that said electric current has a high frequency in the order of ten megahertz, the scanning frequency of said wires being in the order of one hundred kilohertz.
Dependencies are inferred from the claim text.