Abstract: In a facsimile transceiver, an independent, high frequency precision oscillator precisely times the generation of synchronizing pulses which are transmitted to a remote, similar transceiver. An identical precision oscillator assures that the receiver employs the transmitted synchronizing pulse to generate an accurate representation of the information being transmitted. The precision oscillators generate much lower frequency clocking signals, which remain in synchronism during the transmission of a "page" of data.

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).

Abstract: An automatic background and contrast control unit is used in a facsimile transmitter or receiver unit and operates on the uncorrected video signal representing the shade of source document areas being scanned to produce a corrected output signal which accurately and uniformly represents the full range of black and white and intermediate grey areas of the document. The facsimile transmitter makes a preliminary calibrating scan in which it sequentially scans a known black area and a known white area, and the automatic background and contrast control unit fully automatically stores a first sample of the uncorrected video signal when the known black area is being scanned and stores a second sample of the uncorrected video signal when the known white area is being scanned.