WARNING: modification of the factory default settings when the PBX is not connected to a surge-protected, isolated AC power source is undertaken at your own risk. Component damage caused by voltage surges, lighting strikes, brownouts or other power utility problems are NOT covered by warranty!
To modify the BIOS, you will need to connect a USB keyboard and a DVI or HDMI monitor to the back panel of the PBX. Reboot the PBX - see instructions HERE
When the motherboard splash screen appears, press F2 on the keyboard to initiate BIOS contols. Use the arrow keys to navigate to the Power Management screen. Change the setting from the default of Stay Off to Last State. Navigate to the Exit & Save tab, and hit return. Your settings are now stored in the motherboard boot BIOS.