Here is the standard procedure to access this mode, which is common for many Broadcom-based routers like the DSL-2750U C1:
Which (Internet Service Provider) are you configuring this for? What operating system is your computer running? Share public link dlink dsl2750u c1 firmware install
Installing firmware on a is a manual process that requires downloading the correct file from a regional support site and uploading it via the router's web interface. Here is the standard procedure to access this
There are two ways. Using the web interface: go to System -> Configuration and click the Factory button. Using the hardware button: with the router powered on, use a paperclip to press and hold the RESET button on the back for about 10 seconds. There are two ways
This method is a powerful last resort and has been used successfully by many users to restore their routers after a failed flash.