Firmware for a D-Link DSL-2520U ADSL router, with BRU and D in the name probably indicating the regional build and hardware revision, though this is not certain. The 1.85 MB RAR archive likely holds a flash dump used to recover a router that no longer boots or stays stuck with a single light on. Recovery usually means writing the image to the flash chip with a programmer or loading it via the serial console. Check the hardware revision on the router label and save the original flash contents before overwriting.
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 @biosarchive. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →