Color cathode ray tube

In a color cathode ray tube with a single screen containing a plurality of elemental screen areas, comprising:

• a screen provided with a plurality of phosphors emitting colors, said screen being formed by a plurality of elemental screen areas;
• electron gun means positioned facing and corresponding to said respective elemental screen areas, said electron gun means having a plurality of elemental electron gun for generating a plurality of electron beams for successively scanning each respective elemental screen area corresponding thereto;
• a shadow mask assembly positioned facing said screen, said shadow mask assembly including elemental effective regions facing and corresponding to said elemental screen areas, said elemental effective regions having a number of apertures through which said electron beams pass and at least one non-effective region adjacent said elemental effective regions;
• at least one signal source arranged on or close to said non-effective region or boundaries of said elemental screen areas to generate a predetermined signal by an impingement of said electron beams on said source;
• and
• signal receiving means positioned facing said shadow mask assembly to detect said signal from said signal source, wherein the operation of said scanning is based on the detected signal controlling each successive horizontal scanning operation of said plural elemental electron guns, wherein when an electron beam emitted from one of said electron beams impinges on said signal source, said signal generated by said signal source is detected by said signal receiving means, the scanning operation of the electron beam of said one elemental electron gun is stopped, and the scanning operation of another of said plural elemental electron guns is triggered and said another elemental electron gun scans the elemental screen area corresponding to said another elemental electron gun.