Hybrid display system

A colour cathode ray tube (54) has raster scan colour zones defined by X and Y positional signals derived from a stroke vector generator (51) and stored in a digital memory. Raster scan and stroke vector displays are alternately presented in a hybrid display. The display face (10) of the tube is scanned by a plurality of raster lines and a colour transition point is defined by the intersection of a stroke vector with a raster line. The X and Y addresses of the intersection points define the raster line, pixel element, and colour at the transition point. The system is arranged so that the X and Y addresses are provided by the stroke vector generator (51) in synchronous relation with the colour transition points, and read into memory during the stroke vector refresh period. During the raster scan refresh period, the memory contents are recalled in synchronism with the raster scan, passed through a digital-to-analogue converter, and then applied to the display tube to provide filled-in colour zones superposed on the stroke vector display. The reduced memory requirements and controller access time permit dynamically rotating symbology in a synthetic display for aircraft flight instrumentation.