The 2SD1046 is documented in this 115 KB PDF, placed in the schematic group. Its name carries no detail other than the part number. Under Japanese JIS numbering, 2SD parts are NPN bipolar transistors for low-frequency circuits. Repair technicians rely on this kind of sheet to locate the leads correctly before in-circuit testing, to check collector-emitter breakdown and current limits, and to validate cross-reference suggestions so a replacement does not fail under the original operating conditions.
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.