Patent ID: 8059613

Claim:
In a communications system including a first push-to-talk (PTT) network, and a second PTT network having a plurality of interoperability gateways, a method for selecting an interoperability gateway for PTT calls terminated at the second PTT network comprising: receiving a first PTT call request from the first PTT network, the first PTT call request identifying a target subscriber unit on the second PTT network; forwarding the first PTT call request to a first interoperability gateway of the second PTT network's plurality of interoperability gateways; receiving a redirect message from the first interoperability gateway including an identification of the target subscriber and a second interoperability gateway of the second PTT network's plurality of interoperability gateways, wherein the second interoperability gateway corresponds to a location of the target subscriber unit; storing an identifier of the target subscriber and an identifier of the second interoperability gateway in a cache for subsequent use in routing calls to the target subscriber unit; and redirecting the first PTT call to the second interoperability gateway.