Schematic in PDF form for a tone control board labelled NEWGEN TA2411B, where TC most likely stands for tone control. Diagrams like this help you trace the audio signal path, identify the op-amp or transistor stages and confirm component values when you repair or build a preamplifier module. Open it in any PDF reader. Compare the board marking on your actual PCB with the drawing, because small aftermarket audio kits are often sold in several revisions with different layouts.
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 @pdf_servicemanual. 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.