PDF document identified only by the Texas Instruments literature number SDLS115, a code from the series TI uses for its standard TTL logic datasheets. Nothing in the name tells you the exact device, so check the first page of the 102 KB file to see what it covers. A logic datasheet gives you the pin assignments, function tables and timing figures needed to verify a suspect gate or buffer in circuit. It also lists the electrical limits a substitute part must meet before you fit it on a repaired 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 @datasheet_technar_org. 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.