Abstract: A conference station for use in a satellite conferencing system is arranged to receive communications on at least one satellite communication channel having a given frequency and to transmit communications on at least one satellite communication channel having a given frequency. The conference station itself controls whether or not the conference station can transmit on a satellite communication transmission channel by enabling transmission on a communication channel only when the conference station itself determines that that satellite communication channel is free for use or unoccupied. The conference station is also responsive to data signals received from a conference control station to adjust the satellite communication channel frequency or frequencies on which the conference station is able to receive or transmit signal. The conference station may form a part of a group of similar conference stations to which the same communication channels are allocated.