Patent US 4,396,952

Apparatus for evaluating, characterizing and transmitting facsimile data at an efficiency exceeding one transmission bit per elemental scan area but in such a manner as to avoid the drop-out of data which is relatively close in size to an elemental scan area. An illustrative embodiment of one form of the present invention includes an image scanner (50) for line-scanning a document (56) and developing a series of scan data corresponding to the data character of scanned elemental areas of each scanned line, a first storage device (52) for storing a line of scan data, a second storage device (53) for storing a line of previously characterized preceeding line pair data, interpolation logic (54) responsive to the scan data, adjacent scan data previously stored in the first storage device (52) and proceeding line pair data stored in the second storage device (53) and operative to develop present line pair data, and a data utilization device (55) for transmitting, recording or otherwise using the present line pair data.