The 2SB817P is documented in this 30.5 KB PDF, listed with schematics. The 2SB portion follows the JIS system for low-frequency PNP transistors, while the P suffix is not defined by the name and may be a grade or package marker, so read the sheet to confirm. Technicians use such a reference to check the pinout of a power transistor, read its dissipation and voltage limits, and decide whether a complementary or substitute device will fit the heatsink and footprint.
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.