I pointed my Zultys IP PBX at my FreeSwitch installation today and FreeSwitch would not accept calls from it. In the FreeSwitch log is says it is because it "Got no compatible codecs!" ULAW is enabled in the FreeSwitch config and the Zultys system is offering ULAW, but the description that Zultys uses in its SDP looks a little different than it does when a call works through it. Working (Directly from a Zultys 4x4 Phone): m=audio 20000 RTP/AVP 0 8 18 101 a=rtpmap:0 PCMU/8000 Failed (From a Zultys MX250 using the FreeSwitch as trunking proxy): m=audio 20000 RTP/AVP 0 8 18 101 a=rtpmap:0 PCMU/8000/1 Notice the "/1" at the end of the "a" entry on the failed call. I do not know if this is proper or not, but in the interest of interoperability, I thought that I should report the issue. Attached are ethereal traces of a successful call and a failed one along with the FreeSwitch console output from the failed call. If there is a better place to post things like this, please let me know. Sean