text: the general architecture of gsm is maintained in this invention . with reference to fig1 , in addition , a network function is required which is used for registration of the group call attributes , the group call register ( gcr ) 10 a , 10 b , 10 c . the gcr function is mainly a database function , holding information about voice group calls . the signalling between the entities shown in fig1 shall be as defined in the following . the mobile switching center ( msc ) 12 a , 12 b , 12 c containing the cell within which this voice group call is initiated performs subscription checking against visitor , location register ( vlr ) 14 a , 14 b , 14 c and home location register 16 records . it then consults its gcr 10 a , 10 b , 10 c , respectively , to determine the group call attributes related to its msc area and whether it is the group call anchor - msc 12 a for that voice group call . if it is not , the gcr provides with the group call reference and the routing information identifying the group call anchor - msc 12 a to the originating msc . the originating msc then routes the voice group call to the anchor - msc 12 a . if the originating msc is the group call anchor - msc 12 a , along with the group call attributes , the respective gcr 10 a provides information on all group call relay - mscs 12 b , 12 c to be involved . the group call anchor - msc 12 a sets up links to all group call relay - mscs 12 b , 12 c . each msc 12 a , 12 b , 12 c involved in a voice group call obtains its proper group call attributes from the gcr 10 a , 10 b , 10 c related to the respective msc . the gcr 10 a , 10 b , 10 c holds for a related msc area for each group id and cells from which voice group calls can be established by service subscribers , the group call reference to be used for a voice group call to be established and an indication whether the originating msc is the group call anchor - msc 12 a . if the originating msc is the group call anchor - msc 12 a , the gcr 10 a provides the group call attributes related to that group call reference to the originating msc and the originating msc establishes the voice group call . if the originating msc is not the anchor - msc 12 a , the gcr 10 a provides the group call reference plus the routing information identifying the anchor - msc 12 a to the originating msc and the originating msc routes the voice group call to the anchor - msc 12 a . according to the invention , an additional information can be forwarded to all group members during an ongoing voice group call . this is preferably done by transmitting a message containing the additional information on the associated control channel for the traffic channel of the voice group . referring now to fig2 , the msc 12 ( either anchor - or relay - msc ) triggers via an appropriate message , for example , an additional - information - request - message , on the a - interface the base station subsystem ( bss ) 20 to send the additional information to the mobile stations ms 22 , 24 of the group members , that is , one talker 22 and at least one listener 24 . the message contains at least the additional information itself . the vgc - id or vgc - reference represents an optional part of this message . in the case where the message is sent on the controlling sccp - connection ( signaling connection control part connection ) of the vgc , the addressing which vgc is meant is not necessary . in addition to this , the message , that is , the additional - information - request - message , can be sent on the resource controlling sccp - connections . afterwards , the bss 20 transmits the additional information on the sacch of all tchs where the vgc is ongoing , so that the additional information can be received by all ms 22 , 24 participating in the voice group . the provisioning of the additional information in radio cells which are belonging the vgc - area but in which a vgc - channel is not established is not necessary . in the case that the additional information is sent on the controlling sccp - connection , the bss 20 is responsible to transmit the additional information on all sacchs for this vgc . after having sent the additional information , the bss 20 provides an acknowledge information to the msc 12 that the additional information was sent to the mobile stations 22 , 24 . however , this acknowledge information does not confirm to the sender of the message that the individual members of a voice group call have received the message . in order to give an indication that the additional information was at least received by the current talker 22 , the talker 22 may send an acknowledgement on the uplink - sacch for this vgc .