PDF datasheet, revision 7, for the SN74LS640 octal bus transceiver with inverting 3-state outputs, part of the 74LS low-power Schottky TTL range, 71.9 KB in size. It documents the direction and enable controls, pin assignments, drive capability and switching characteristics. On vintage computer and controller boards this chip often sits between a data bus and peripherals, so the sheet helps when checking for stuck bus lines or a shorted transceiver. Note the inverting outputs before substituting a non-inverting relative.
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.