I'm setting up a UC520. I have one analog line from POTS that is dedicated to fax. I have terminated that line on FXO interface 0/1/3. I have ran an analog telephone line from my fax machine and terminated on FXS port 0/0/0. I can make out fax ok, but when I try to fax in, the fax machnie rings, then answers, but no fax transmission. If I take UC500 out of picture and terminate pots line on fax machine directly, it receives fax ok. Am I missins a config somewhere?