Handsfree circuit page from the Samsung SM-A05 schematic, a 2.85 MB PDF. It deals with the headset jack: detect line, left and right audio outputs, headset microphone path and the protection parts near the connector. Useful when wired earphones are not recognised, play in one ear only or the headset microphone fails. Trace the lines with a multimeter against the drawing and check the detect switch. Opens in any PDF reader. Check the handset is really an SM-A05 before working from it.
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.