Patent GB-1058230-A (GB)
Title: Xerographic facsimile system
IPC: G03G15/30
Filed: 1963-11-25
Abstract: 1,058,230. Xerographic facsimile transmission systems. RANK XEROX Ltd. Nov. 25, 1963 [Nov. 26, 1962; Sept. 3, 1963 (2)], No. 46499/63. Heading H4F In a facsimile communication system both the transmitting and receiving stations are provided with oscillator means together with filter and detector means whereby supervisory and control tone signals may be exchanged between the stations for regulating their operations. The invention is described as applied to a system in which at the transmitting station a document to be transmitted is traversed by a conveyer belt past a cathode-ray tube flying- spot scanner which is scanned in the transverse direction only, and the video signals are generated by a photo-multiplier tube responsive to the reflected light. At the receiving station a facsimile of the document is produced by a xerographic recorder comprising a rotating photo-conductive drum which is given an initial surface charge by a corona discharge device and then selectively discharged by light from a transversely scanning cathode-ray tube, the beam intensity of which is modulated in accordance with the video signal from the transmitter. The resulting charge pattern is developed visually by toner material which, as the drum rotates, is subsequently transferred by a charge transfer process on to a paper web and fused thereon by passage of the web over a heated roller. The drum is thereafter cleaned and cleared of all charge by exposure to a corona discharge, contact with a web of cleaning material and finally illumination by a light source. To maintain the cathode-ray tubes at the two stations scanning in synchronism, scanning synchronizing signals in the form of bursts of sinusoidal signal are added to the transmitted video signal between each transverse scan. The signals control the receiver scanning by way of an automatic frequency control system which also furnishes gatecontrol signals to separate the video and synchronizing signals. The receiving station is provided with a number of switches responsive to the condition of components in the receiver. When the drum is in its proper operating position, the paper supply is not broken, the paper supply is ample and the web cleaner is of sufficient length, an input is provided to an AND gate. Other inputs are provided when the filament of the cathode-ray tube is sufficiently heated and the heated fuser roller is at its operating temperature. A further input to the gate is provided for a control signal sent fom the transmitter, so that when the control signal is received and when all the receiver components are in a condition for operation, an output is provided from the gate which causes the transmission of a control signal back to the transmitter to indicate that the receiver is ready for operation. A signal from the receiver may be used to initiate document feeding at the transmitter., Some receiver operations may be initiated upon reception of synchronizing signals. A signal from the transmitter may indicate that the end of a document has been reached and may cause operation of a paper cutter. The control signals may be multiplexed with the video signals or sent over separate channels.