US Patent 7154638 Printed page tag encoder

A printed page tag encoder has an input at which to receive a tag structure template, an input at which to receive fixed data bits, an input at which to receive variable data bit records, and a tag dot generator outputting single bits depending on position in the tag defined by the tag structure template and said fixed and said variable data. The encoder additionally has a redundancy encoder for optionally encoding said fixed and/or said variable data. The redundancy encoder utilizes Reed-Solomon encoding. Tags are placed regularly on a page and ideally in a triangular grid.