Abstract: In a variable speed facsimile transmitter employing a storage mode photodetection array as a line scanner, the array is driven at one of a plurality of selectable clock rates so as to generate a video line signal in response to each clock pulse. The photodetection array is discharged at an instant delayed from the occurrence of the clock pulse by an interval determined by the difference between the selected clock rate and the highest clock rate to discard the video signal available at that instant and then allowed to develop charge during the rest of the interval between clock pulses, whereby a constant magnitude video line signal is derived at the occurrence of each clock pulse regardless of the selected clock rate.