Abstract: To set-up a dispatch call, a controller identifies the destination units, destination sites, controlled devices and paths needed to support the call, and which LAN bridges will be used to create the communication paths. The controller then assigns the controlled devices a temporary address identical to the permanent address of one of the controlled devices, and then informs the LAN bridges which LAN ports should carry messages containing the temporary address. With all controlled devices having the same temporary address, and with the LAN bridges ready to pass messages containing the temporary address along a chosen path, the controlled device assigned to support the call request can transmit the messages generated by a source communication unit to other controlled devices using the temporary address. Thus, only one representation of a message produced by the source communication unit is transmitted from the assigned controlled device.

Abstract: A method and a mobile communications system for maintaining group data relating to a communication group in a mobile communications system including a plurality of exchanges. To optimize the management of group data, one of the exchanges is selected as a main exchange, in the database of which a master copy of group data of the communication group is maintained. Information is maintained in the database of the selected main exchange on exchanges of a fixed distribution area. The group data are stored in the databases of these exchanges irrespective of the location of the subscribers. Information is maintained on exchanges of an enlarged distribution area. The group data are stored in these exchanges if subscribers belonging to the communication group register under the exchanges. Information is maintained on exchanges of a current enlarged distribution area. Subscribers of the communication group are currently registered under these exchanges.