Part datasheet for the 2SD1140 in a 159 KB PDF, listed as a schematic though the name contains only the transistor number. The 2SD prefix indicates, under Japanese JIS rules, an NPN bipolar transistor meant for low-frequency circuits. Expect maximum ratings, electrical characteristics and package drawings. A technician consults it when a stage has failed, to read the correct pinout and the specifications that any replacement or cross-referenced equivalent has to satisfy.
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.