Datasheet for the SN7402N quad 2-input positive NOR gate, part of the classic TTL logic family and packaged in plastic DIP. The roughly 14 KB PDF lists pin assignments for all four gates together with supply and output limits. A repairer uses it to confirm which pins form each gate and to check that outputs go low whenever an input is high. Any PDF reader will open it; before trusting the figures, verify the exact part number and suffix printed on the chip being tested.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.