Patent ID: 7583659

Claim:
A media gateway, built in an exchange capable of accommodating a plurality of Public Switched Telephone Network (PSTN) telephones, for performing conversion between voice signals and IP packets, said media gateway comprising: a media gateway control unit connected to a control unit of the exchange; an IP network interface connected to an IP network; a first protocol processing unit for executing a call connection procedure according to a first call control protocol by communicating messages with an IP call connection controller on said IP network via said IP network interface; and a second protocol processing unit for executing a call connection procedure according to a second call control protocol by communicating messages with said IP call connection controller via said IP network interface; wherein said media gateway control unit instructs said first protocol processing unit to start call connection processing according to the first call control protocol in response to a call connection command issued from said exchange control unit when a call is originated from any of said PSTN telephones, aborts the call connection processing of said first protocol processing unit while maintaining the connection between the PSTN telephone and the media gateway when receiving a connection protocol change command from said IP call connection controller via said IP network interface before completing the call connection according to the first call control protocol, and instructs said second protocol processing unit to start call connection processing according to the second call control protocol.