Datasheet in PDF form for the SN7420N, a standard TTL dual 4-input positive NAND gate; the N suffix denotes the plastic DIP package. At under 7 KB it is a very short document, likely covering pinout and basic ratings rather than full characterization curves. Technicians consult it to confirm which pins carry each gate's inputs and output, plus VCC and ground, when probing logic on older boards. Verify the exact marking and suffix on the chip before treating the data as a match.
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.