Compact datasheet, 14.5 KB in PDF form, for the part numbered 2N2955 according to the file name. At this size it is likely a short summary page listing the main electrical limits and pin assignment rather than a full multi-page document. Use it to verify polarity, case connections and voltage and current ratings before replacing a failed transistor in an amplifier or supply. Because the name gives no manufacturer, cross-check figures against another source and the marking on the original part when ratings are critical.
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.