I have another problem with the setup of grandstream 4104. Maybe I should have gone with the patton. I looked in the forum and on the web for similar problem. Some people have clicked the setting "PBX Delivers Audio". I did that under the extension setting and under the PSTN settings but I still have: -Terrible call quality -Some keys ( e.g. the * to access my cell phone voicemail ) do not work. I spent 3 days on this setup ... a bunch of issues.... Any suggestion?!