Touch screen circuit sheet for the Samsung SM-A21s, a PDF schematic of 3.82 MB. It shows the display and touch connector side relevant to the touch panel, typically the touch supply and communication lines. A technician uses it when touch is dead or erratic after a screen replacement, measuring voltages at the connector, checking for shorted filter parts and tracing lines to the main board. Any PDF viewer opens it. Make sure the phone is an SM-A21s, since the regular A21 and other models use different boards.
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 @phoneSchematics. 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.