Schematic archive, 4.93 MB zip, for a device identified only as 5130; given the numbering this is most likely the Nokia 5130 XpressMusic, but the name gives no brand or RM code, so confirm after opening. Service diagrams of this kind show battery and charger circuits, the power management chip, audio, keypad and display connections with part designators. They help when tracing a no-power or no-charge fault, locating test points and checking components for shorts. Compare the hardware label on the phone with the pages.
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 @esquematicosparatodos. Enginerys does not host this file.
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Compressed archive that every operating system opens without extra software.