I'm currently using the 3CX softphone for Windows connected to a Mitel 3300 PBX. IP is only running between my phone and PBX. The PBX communicates with the PSTN via a PRI/T1. I can make calls to other internal extensions and audio works in both directions. If someone calls me from outside (through the T1), audio works in both directions. If I call out to someone (again through T1), I can hear them but they can't hear me. Any ideas? The only thing that might be an issue is that my computer sits on a different subnet than my PBX. My PBX is on a 192.168.5.x network and my PC is on a 192.168.0.x network. A Fortinet firewall joins these two networks, but we have set all traffic to be wide open. Any thoughts?