A 277 KB PDF covering the 2SD2539, a part number in the JIS 2SD family, which denotes NPN bipolar transistors for low-frequency circuits. Although indexed as a schematic, it is probably the manufacturer datasheet. It is useful for checking pin assignment before testing the junctions with a multimeter in diode mode, and for reading breakdown voltage, collector current and dissipation limits. When choosing an alternative part, match polarity, ratings and footprint, not just the general type.
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.
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