How To Reset a Digium Phone Using the Keypad
Steps:
Reboot the phone by unplugging it and plugging it in again after 10 seconds.
During the boot up screen (where it counts through the steps 1 thru 8) wait until you see step 2 of 8 on the LCD screen.
Once it says step 2 of 8, press and hold the *, 8, and 6 keys simultaneously on the phone's keypad.
You will see a message come up that the phone is resetting to factory defaults. Release the keys.
The phone will reboot, and it will come back up normally.