PDF datasheet for the 2N3771 at 42.8 KB, labelled schematic but naming a single 2N-series transistor rather than a device board. No manufacturer or revision is stated in the name, so treat it as one vendor's version of the part's specifications. A repair technician reads it for pinout, case drawing and limiting values when diagnosing a shorted junction or selecting an equivalent. Opens in any PDF reader; figures may differ slightly from other vendors' sheets for the same number.
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.