phone traffic (Campanella, 1978). 1984). Satellite switched TDMA is available with INTELSAT VI satellites It would be ideal for INTELSAT users if a single satellite in each to enable up-beam or down-beam connectivity to be optimised. ocean region had enough fully interconnected capacity to carry all However, most INTELSAT transponders are operated in the of the traffic that the region requires. Successive series of INTEL- FDMA mode, with various modulation method, analogue and digi- SAT satellites have had larger capacities, satellite antenna beams tal. Multiplexed analogue systems use FM and FDM, with stand- have been kept wide to maximise connectivity and the required ardised basebands of various capacities, the structure of the figure of merit (G/T) of earth station antennas has been kept high to baseband being related to the CCIR and CCITT standards for maximise per-satellite capacity. However, demand per region has analogue radio relay system basebands. The deviation and power outpaced capacity per satellite consistently since 1967. There are level of the carriers are optimised to give channels which attain their currently 13 operational satellites, of the INTELSAT V, VA and VI performance objectives with economical use of transponder power series, seven of them serving the Atlantic Ocean alone. In each and modulator allotments of bandwidth. Most digital systems use ocean region, one satellite is designated as the Primary Satellite and TDM and 4-phase PSK, with channels 8-bit encoded, although every country is allocated some capacity in it, SO that earth stations single channel PSK systems are also used. with a relatively light total traffic flow can get access to all the Another important function of the INTELSAT global network is routes of interest to them within their own ocean region without to provide temporary, brief wide band links for the transmission of using more than one antenna. If the capacity required between two news, in the form of television pictures, from the scene of origin to earth statio