Datasheet for the 2sb1566 PNP bipolar transistor in a 37.5 KB PDF. The 2SB label, per the JIS convention, means a PNP device for low-frequency circuits; the file name says nothing about manufacturer, package or revision. Technicians consult a sheet like this to identify leads, verify voltage, current and power limits, and decode the marking printed on the body. That allows a reliable diode-mode test and a sensible choice of replacement. Confirm the board part carries the matching code 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.