Satellites orbiting the earth are used to receive and retransmit signals for telephone, television, radio, and data communication. The basic relay device in satellites, the transponder, has seen tremendous increases in efficiency thanks to advances in compression technology. A communications satellite system comprises the satellites and the ground stations for transmitting and receiving the signals. Direct broadcasting satellites, which are geostationary, transmit radio and TV services that consumers can receive through a cable redistribution network or a personal domestic disc antenna. Recently a digital satellite radio system was inaugurated using satellites over Africa, the Middle East, Asia, and Latin America. Signals from these satellites—including distance education programs that are planned—will be able to be received directly on special portable radio receivers. Communications satellites resources   Kondo, K., 1996. "Inter-University VSAT Network in Japan: Space collaboration system." Paper presented at the conference on Educational Technology 2000: A Global Vision for Open and Distance Learning, Singapore, August 15-17, 1996.

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