At 198 KB, the PDF for the 2SD1658 is one of the larger sheets in this group, though it still names only the part. JIS numbering gives 2SD to NPN bipolar transistors for low-frequency or power circuits. The extra size may mean more curves or package options, but that is not stated. Use it to identify base, collector and emitter, read maximum ratings and gain classes, and assess replacements. Filed as a schematic, it describes a component, not a circuit 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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.