Patent ID: 7679607

Claim:
An electronic whiteboard comprising: a writing input portion having a surface writing layer, an under layer, an input induction layer disposed between said surface writing layer and said under layer, and an output; a control circuit connected to said output of said writing input portion; and a covering frame formed around peripheries of said writing input portion; wherein said input induction layer has a plurality of electromagnetic induction layers overlaid one another and position reference columns provided around said electromagnetic induction layers, and each electromagnetic induction layer has a wire lattice comprising: first wires winded on said wire lattice, each of said first wires being winded around said position reference columns with multiple turns to form a plurality of loops with a plurality of latitudes substantially uniformly distributed across said wire lattice; second wires interlaced with said first wires, each of said second wires being winded around said position reference columns with multiple turns to form a plurality of loops with a plurality of longitudes substantially uniformly distributed across said wire lattice; and a plurality of induction cells each induction cell being a space surrounded by two adjacent longitudes and two adjacent latitudes; and wherein said first wires and second wires are enameled wires that are entirely covered or coated by an insulating layer and are insulated from each other, the induction cells of one electromagnetic induction layer overlay and interlace with the induction cells of another electromagnetic induction layer, and the size of each induction cell on one electromagnetic induction layer is different from the size of each induction cell on another electromagnetic induction layer.