20110305188 | FAST INTER SYSTEM PUSH TO TALK OPERATION - A method for establishing a press-to-talk (PTT) session between a first terminal serviced by a first communication system and a second terminal serviced by a second communication system, in which the first communication system and the second communication system are interconnected by a transmission link. The method includes receiving a transmission demand message (TX-DEMAND) from the first terminal, sending a transmission granted message (TX-GRANTED) to the first terminal and a transmission demand message (TX-DEMAND) to the second communication system if a communication channel is locally available for the press-to-talk session, receiving transmission packets from the first terminal and relaying the transmission packets to the second communication system, and then, continuing relaying transmission packets to the second communication system if a transmission granted message (TX-GRANTED) from the second communication system in reply to the transmission demand message (TX-DEMAND) is received. | 12-15-2011 |