Filed among schematics, this 118 KB PDF is identified solely by 2SC3451, a Japanese JIS transistor number. The 2SC prefix marks an NPN bipolar device, so expect a datasheet covering pinout, absolute maximum ratings and typical curves. It is handy when diagnosing a dead stage, letting you check junctions in circuit with the right probe placement, and when sourcing a replacement with matching or better limits. Confirm the full code and any suffix on the actual component first.
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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.