Modify Modify Read (MMR) compression is the name given to the compression algorithm specified by two-dimensional CCITT recommendation T.4 to increase transmission speed making the fax machines more effective. Modify Modify Read allows greater number of lines to be coded by MR than in T.4. T.6 makes the assumption that the transmission is over a circuit with a low number of line errors. In this case, there is no maximum number of lines for which the differences are encoded.