[sip-comm] problem



I am doing a project in voip.I tryied to use Sipcommunicator for connecting to

pc to phone : the phone is ringing .but i cant speak or hear any response..
                    invalid numbers are reported..

pc to pc : i have made changes .. same problem persits i cant hear.. thru my head phone

is it because of any problem with my head phone or bec any other reason

do mail back ...it is very urgent
                              thank you


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