Indicates that the transmit audio channel has been closed.

The occurrence of StopTx indicates that the remote endpoint has specified to the application server that the transmit RTP audio stream should no longer be sent.

StopTx does not occur until either AnswerCall or MakeCall has been used in a script. This event can occur if the call is placed on hold by the remote endpoint, if it is transferring the call elsewhere.

If this event occurs for a call not currently in a peer-to-peer relationship, then the media engine will stop transmitting audio to the destination with the connection accordingly.

StopTx will still occur for calls currently in a peer-to-peer relationship. However, because there is no media engine connection associated with such calls, the MmsId and ConnectionId event parameters would be empty in that case.

The Call Control API makes every effort to abstract the complexities of the underlying telephony protocol; however, one should consult the Call Control Feature Matrix to understand what Call Control actions and action parameters are valid for each of the four supported protocols. One can set installation and deployment guidelines based on the Call Control actions and action parameters that an application uses; the Call Control Feature Matrix makes developing such guidelines feasible.