Communications satellites allow telephone conservations, telegraph messages and radio and TV programs to travel from one part of a country to another or even across oceans. They also can handle huge amounts of data. For example, all the files and records from a computer in the United States can be sent to a computer in Europe via satellites stationed over the Atlantic Ocean also can handle about 30,000 phone calls at one time. Without satellites, extensive networks of wires or cables would be needed to achieve lite broadcasts can reach a large number of people at the same time.
Most communications satellites are built, launched and operated by large companies or Government agencies. Some communications satellites are used by only one country for transmissions to and from areas by only one country for transmission to and from areas within such domestic satellites. As many as 50 countries now operate satellite systems. The Aussat satellite system in Australia combines telecommunications with a direct television broadcasting system. India and China also have been able to install nationwide communications systems using satellites.
Some communications satellites are shared by several countries. Many of these satellites function as a network. The satellites in such communications satellites systems are designed to relay signals among themselves as well as to the ground. In this way, signals can be transmitted around the world. For example, more than 140 countries used the service of the INTELSAT system, a network of communications satellites that reach more than 600 earth stations worldwide. Other communications satellite systems include Eutelsat, which serves a number of European nations, and Arabsat, used by Arab league.
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