PURPOSE: To realize a demand assign-digital sound insertion satellite communication system of small allotment frequency and easy to control by allotting number of usable channels of each ground station from the number of up aural signal channels of all ground stations.

CONSTITUTION: The receiving device 3 of a ground controlling station N receives a burst from all ground stations A∼C and sends the signals to a receiving circuit 6. The receiving circuit 6 reports connection control information and an average value of the number of channels in a fixed time in up-sound signal transmission of each station of a controlling device 7 from a connection control signal of each station. The controlling device 7 controls unitarly outgoing, incoming etc. of each ground station based on control information received from the receiving circuit, and at the same time, compares the number of channels in sound transmission of each station and the number of usable channels alloted last time. When the ratio exceeds a standard value, distribution to other station is changed, and this distribution information is reported to all stations as connection control information.