Datasheet-type PDF of 308 KB for the 2SD2553, filed under schematics. The Japanese JIS designation 2SD identifies an NPN bipolar transistor intended for low-frequency applications. Only the part number appears in the name, with no maker, package or revision. The larger size suggests extra graphs or drawings. Technicians use it to confirm lead assignment, read maximum voltage, current and dissipation figures, and check that the code printed on the fitted part matches before relying on the data.
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.