Service manual schematic from Sony for the MEX-BT2500 car audio receiver, version 1.0, in a 5.00 MB PDF; the sm tag points to a service manual. It typically includes block diagrams, schematic sheets, board layouts and parts lists. Useful for tracing battery and ACC supply lines, amplifier IC faults, CD loader or tuner issues and Bluetooth module connections. Open in any PDF viewer, and since this is the first revision, compare values on the board itself where a later issue might differ.
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 @datasheets1. 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.