The 2SC3153 is the subject of this 98.0 KB PDF, catalogued as a schematic though the name points to a discrete-part data sheet. JIS coding puts it in the 2SC family of NPN bipolar transistors, normally marked C3153 on the body. Expect electrical characteristics, absolute maximum ratings and a package drawing. A repair technician uses it to verify the pinout before in-circuit diode tests, to check that a proposed equivalent meets the voltage, current and power ratings, and to confirm the lead spacing fits the board.
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.