Abstract: Disclosed herein is a facsimile transmitting apparatus including a sensor for detecting the dark/light variations in a document and a transmitter for generating and transmitting transmission signals including signals representing those dark/light variations. The transmitting apparatus further includes a receiver for detecting received signals including an interrupt signal of predetermined frequency. Control means are coupled to the transmitter and to the transceiver for interrupting transmission upon detection of the interrupt signal. The receiver includes a means for subtracting the transmitted signal from the received signal so as to generate a difference signal. Transmission is interrupted if the difference signal comprises the predetermined frequency.

Abstract: The scanning mechanism of facsimile transmitter and receiver units are synchronized by comparing the relative positions of each of the scanning mechanism at a particular time. A variation in the rate of the scanning motion for one of the scanning mechanisms is then initiated and this variation is continued until a predetermined time corresponding to a substantial degree of coincidence in the scanning position of each of the scanning mechanisms. The variation in the rate of the scanning motion is a substantially ramp-like function of time.