Reference PDF for the HCF4050B, a non-inverting hex buffer from the CMOS 4000 family, as the file name itself states. At 175 KB it is likely the full manufacturer datasheet with pin diagram, supply ratings and switching data. The 4050 is commonly used as a level shifter because its inputs tolerate voltages above its supply, so the sheet helps when tracing a signal between logic domains, checking each of the six buffers with a meter or scope, or picking a CD4050 substitute.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.