Abstract: Provided is, for example, a push-to-talk over cellular (PoC) system including a first mobile terminal, a second mobile terminal, and a management center apparatus, in which: the first mobile terminal includes a first wireless communications circuit to receive a PoC communications start response including an identifier of the second mobile terminal from the management center apparatus, and a PoC communications circuit to communicate with the second mobile terminal through PoC communications; the second mobile terminal includes a second wireless communications circuit to transmit a group-participation request including the identifier of the second mobile terminal to the management center apparatus; and the management center apparatus includes a controller to register the identifier of the second mobile terminal.