HI

I have developed an application in Microsoft RTC API that uses SIP to make outbound calls to the PSTN. When the call connects, no sound can be heard on either end. I have to make a sound before the channel is opened and then the conversation can take place. Why is the sound & mic not automatically opened

To explain a little more- the call is placed and i get the in progress event, but there is no sound of the ringing phone. If i remain silent, and the person picks the phone up and says hello then i can't hear them. However, if i make a sound down the mic as the in progress event is recieved then i can hear the ringing tone and when they answer i can hear them and talk as normal.

Can anyone tell me what's going on

Thanks

Tom