Abstract: A facsimile transmitter-receiver system which is adapted for use over a limited band width transmission path employs a redundancy reduction unit to speed-up transmission time by rapidly sweeping the transmitters single scanning beam in full or partial search passes across proposed data free areas of a source document. In the horizontal direction a transition to partial fast search during a horizontal pass is made beyond a proposed right hand data boundary and is accompanied by a one line space temporary downward deflection or bias of the scanning beam, which facilitates search for new data boundaries and also permits the system to make a slow scan retrace of a line (by eliminating the bias whenever data is actually found in the search pass).