Small 72 KB PDF giving the specifications of the 2SD2120 transistor, an NPN type by its Japanese JIS prefix. No device or board is tied to it by name, so treat it as a general part reference. Technicians use it to read pin assignment, breakdown voltages, collector current limit and gain range when diagnosing or substituting the transistor. Cross-check the marking on the fitted component and measure junctions with a multimeter to confirm the fault before ordering parts.
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.