Importance

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Abstract

Method and apparatus for controlling the display of a raster scan color cathode ray tube. The tube is provided with an orthogonal array of picture elements (pixels) with each picture element having a unique binary address. An addressable memory having memory locations with addresses corresponding to those of the picture element has stored in such memory locations an address of a location in a color look-up memory for an alphanumeric color, for a graphic color and priority signals. In the color look-up memory at the addressed locations is stored binary signals representing the color and intensity of a pixel. In synchronism with the raster scan of the picture elements of the cathode ray tube, there is read from the memory graphic color addresses, alphanumeric color addresses and priority signals for each pixel. One of the addresses, either the graphic or alphanumeric, is applied to the color look-up memory, with the address that is applied being determined by the binary priority signals. The binary color signals stored at the addressed color look-up memory location represent varying intensities of a plurality of predetermined colors. The color signals are converted by a digital to analog converter into analog signals which are applied to the color cathode ray tube to control the color and intensity of each pixel as it is scanned.

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First Claim