Abstract: For controlling the direction and rate of movement of an image on a raster scan display, a first set of counters is arranged to generate digital pulses for use as horizontal and vertical sync pulses for use in conjunction with a video adder for controlling the image on the display. Means, such as a second set of counters, driven by another clock means, provides an output which is compared to that of the first named counters to provide information signals to the video adder for controlling the location and movements for the image being displayed.