PoC server, the PoC terminal, control method and plant control method PoC terminal

A floor can be fairly acquired in a PoC communication. In the PoC server which controls a floor in a PoC communication, a floor is put in an idle state in a PoC communication after a session establishing process required in the PoC communication. The information about the floor idle state is notified to terminals TA and TC which perform the PoC communication. When the PoC communication is initiated, the idle state of the floor is simultaneously noticed to both calling and called users, thereby realizing fair acquisition of a floor.