FACSIMILE ENCODING AND THE INFLUENCE OF TRANSMISSION ERRORS.

Most facsimile devices or ″remote copiers″ presently in use employ techniques for conversion of black-and-white pictures into electrical signals, which result in a sequence of pulses, where every pulse can represent one picture element (pel). During transmission of such a signal via telephone lines disturbances may occur. To decrease transmission time it is necessary to employ some kind of coding which reduces the redundancy inherent in practically every document. A technique for reducing the amount of data to be transmitted in a facsimile system with two levels of brightness is described which is called runlength coding (RLC). A code is proposed which has practically the same compression factor as e. g. a modified Huffman code, but will preserve unchanged nearly all runlengths, which are following the decoded runlengths of the corrupted codeword. This code is called ″Intermediate Ternary Code″ (ITC).