Abstract: A two-valued object field is scanned and stored on a line-by-line basis and sequentially read out on a block-by-block basis. Each block has an equal number of signal components each representing the light values of the two-valued object found along a line path. Means are provided for encoding the signal blocks to produce a first code when the signal components are entirely at white level, a second signal when the signal components are entirely at black level, and a third signal when the signal components are of a mixture of black and white levels. The first and second codes are transmitted while the respective signal components are inhibited. The third signal is transmitted followed by the associated signal components.