File for the 2N3904 with a _3 suffix, 51.2 KB PDF; the suffix probably distinguishes it from another copy or edition, but the name does not state its meaning. Filed as a schematic, it should be a datasheet for this common JEDEC-registered part. Use it to look up pinout, case outline, maximum ratings and gain data during troubleshooting or when sourcing a replacement. Compare it with the other 2N3904 sheet in the index and confirm the package on the board before trusting the lead order.
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.