Combined datasheet for the BC546 and BC547 NPN small-signal transistors, packaged as a 57.5 KB PDF. The document normally sets out ratings for each type, which differ mainly in collector voltage, together with gain groups, package outline and pin assignment. Repair technicians use it to confirm leads before soldering, to check whether one variant may substitute for another, and to match a complementary PNP part. Read the voltage column carefully when substituting, and verify the pin arrangement against the footprint on the actual board.
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.