Application note related to the XR2206, the Exar monolithic function generator IC, saved as a 145 KB PDF; the number 2 in the name suggests it is the second note in a set on this chip. Such notes show typical circuits for sine, square and triangle output, frequency setting with the timing resistor and capacitor, and amplitude and FM or AM modulation. A technician repairing a signal generator or test instrument built around this chip can compare the board circuit with the reference design and check pin voltages and component values.
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. 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.