Conference calls in mobile networks

Conference calls in a GSM network are provided by processing incoming speech from participants 10-13 in a conference bridge 18 including a voice activated detector 19, which can distinguish silent periods. Speech components are encoded by a multi-channel variable bitrate coder and sent through a multi-channel link 20 to a receiving terminal 14. Non-speech components are coded as a silence signal to reduce transmission bandwidth requirements. At receiving terminal 14 voice components are passed to a spatial processor, which distinguishes between source participants by the channel containing the coded speech. Each participant's voice is located at a spatially separated location, to aid identification. The spatial processor may alternatively be located within the network, which sends stereo signals to the terminal 14.