An exemplary gateway apparatus provides push-to-talk (PTT) communications between users in one network with users in another network where the networks utilize different communication protocols. It includes two protocol modules that interface with the two networks, respectively. The protocol modules...http://www.google.com/patents/US7974650?utm_source=gb-gplus-sharePatent US7974650 - Interoperability between different types of wireless networks for push to talk group calls
