CD4066 reference document, a 174 KB PDF for the CMOS quad bilateral analog switch. Listed as a schematic, though it is most likely the datasheet with pin diagram, on-resistance figures and control logic. Technicians use it to find which control pin enables each switch, check that analog or digital signals pass when the switch is on, and measure on-resistance when audio or signal routing fails. The 4066 is widely second-sourced, so pinouts usually match other makers.
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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.