asterisk users - Aug 2003 - No Audio on SIP Phone Connection

Hi,

I have eStara SoftPHONE software loaded on 2 PCs. Both SoftPHONEs
successfully login into Asterisk SIP Proxy and make a phone connection. But
there is no audio communication in this connection. I turned on SIP
Debugging on Asterisk. There is no any debug message when I talked to the
SoftPHONE. I would appreciate it if you could tell me what configuration I
might miss.

Thanks,
Kang