Patent ID: 7567816

Claim:
A radio communications system comprising a plurality of communication terminal devices for performing radio communications with a press-talk switch, a server for establishing radio communication processing among said communication terminal devices, and a plurality of Closed User Group servers for controlling said communication terminal devices for establishing said radio communication processing, said server and said Closed User Group server respectively being owned by different companies, wherein said Closed User Group server has: group information storage means for making a group among particular communication terminal devices to implement radio communication with said press-talk switches, and storing group information where Closed User Group identification information for identifying Closed User Group servers is given to the made group, said communication terminal device has: radio communications group acquisition means for acquiring, from said Closed User Group servers, the group information among particular communication terminal devices for implementing radio communication with said press-talk switches; and audio information notification requesting means for transmitting to said server, together with said group information, an audio information notification request for notifying audio information to a second communication terminal device in the group information acquired by said radio communications group acquisition means, and said server has: radio communications establishment means for acquiring, on receipt of the audio information notification request from said communication terminal device, based on the Closed User Group identification information in the group information received together with said audio notification request, the group information of said communication terminal device from said Closed User Group server, establishing radio communication among the communication terminal devices in the acquired group information, and transmitting audio information to the second communication terminal device in said group information.