Patent ID: 8886242

Claim:
A method of operating a push-to-talk communication between a Push-to-Talk communication system (PoC) group comprising at least one member of a first communication network operated by a first network operator, and a PoC group comprising at least one member of a second communication network operated by a second network operator, by using a PoC application server in each communication network, the method comprising: (a) connecting the at least one member of the PoC-group of the first network with the members of the PoC-group of the second network for push-to-talk communication; and (b) synchronizing the PoC application servers of the respective networks so that the group members of both networks are known to both operators; wherein the synchronization is carried out whenever a user requests an update of all group members of the PoC groups before sending a PoC message; and wherein step (b) comprises the steps of: (c) using an application server of a member of the PoC-group of the first network that is logged onto the first network as a proxy for an application server and contact for a member of the PoC-group of the second network; and (d) also using the application server that is used as a proxy as a partial PoC group server and contact for all members of the PoC-group of the second network that are logged onto the second network.