quote from : (dvdhack.com)

3. Cyberhome AD-N 212

How to convert your Cyberhome AD-N 212 player into a multi-region compatible machine

This hack also works on the Cyberhome AD-M 512 player

To convert this player to Multi-Region

1. Open the drive tray

2. Press the 7 button on your remote control

3. Press the 6 button on your remote control

4. Press the SEL button on your remote control

5. You will now enter the hidden setup page, and can change the player to any Region or set it to Region Free by entering 13 as the country code.