1.This paper describes the principle, scheme and implementation of error control for Group 3 document facsimileapparatus, based on CCITT recommendation on the standard of error correction mode(ECM) for Group 3 apparatus.
2.It is shown that,if the scanning resolution meets the recommendation by CCITT on G_3 and G_4 facsimileapparatus,then the visual-perception effect of the two-level rendition by comparison with the Bayer ma-trix is almost the same as that of the original half-tone pictures.
