I am using a grandstream gxw4104 PSTN gateway. When making outbound calls from voip to pstn, call quality is fine. Very responsive both directions. On inbound calls from the pstn to voip, there is a delay in the audio from when someone speaks to the other person hears of about 1-2 seconds. I have upgraded the firmware on my phones and gateways but still same problem. I can provide more info if needed. I am wondering if this is an issue with the gs gateway and if others have experienced simliar issues. I have a ticket open with gs as well but they are not much help.