The 2N4126 is the subject of this 81.9 KB PDF, listed in the schematic section of the catalogue but almost certainly a single-part datasheet. Nothing else, such as vendor or revision, is given by the name. A sheet of this kind lets a technician look up pin order, package drawing and rated limits, which helps when diode-testing junctions in circuit or picking an equivalent from a parts bin. Check that the case style on the board matches the outline shown before relying on the pinout.
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.