Small PDF filed under schematics whose name only reads 1B series, so the exact part or device it covers is not stated. The naming resembles a datasheet for a family of discrete components, possibly diodes or small parts sharing a 1B prefix, but the file itself must be opened to confirm. At 56.3 KB it is likely a short document of a few pages. Technicians usually consult such sheets for pinouts, package markings and electrical ratings when identifying a replacement part, so compare the marking on the board with the tables before substituting anything.
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.