Mitch,
thanks for your reply. I did change sip port to 5061 and other values as well. In fact my router here did not allow port forwarding to the radio control unit as it had 5060 internally forwarded to something else already, so it would come up with a warning message. Any other ports that I have tried worked, though. What I can't understand is that the setup was working flawlessly from one internet remote location but does not now from a different one. I have also used the network at work to try it from there: again no audio. I almost feel that there is something amiss at the radio site, an audio connector fault from the radio to the remote unit perhaps, because with certain audio quality settings (setting 0, for instance) I get hiss out of the speaker here, but no audio...I guess I will have to be patient until Friday which is when I will be returning to the radio site. Again, thanks for your help,
Rainer