PDF of 1.44 MB named HT7166, catalogued under schematics, with no device, brand or board stated in the name. The name resembles a component part number, so the contents are likely a datasheet or application circuit for that chip. Read it in a standard PDF viewer to check pinout, operating voltages and recommended external parts when diagnosing or replacing the device. Verify the actual marking on the chip matches HT7166 before relying on the figures.
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 @datasheets1. 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)