Filed under schematics, this 169 KB PDF refers to the 2SC2290, an NPN transistor in the Japanese JIS 2SC series. Its content is most likely the manufacturer datasheet. When servicing equipment, technicians check its absolute maximum ratings, hFE grading and package pinout to confirm a fault or select an equivalent. Compare the marking and case of the original transistor with the drawings here before soldering in a replacement, and verify the base, collector and emitter positions.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.