Communication satellites are normally geostationary satellites. They have devices called transponder which receive signals from an earth station and transmit them in different directions. The signals in the form of electromagnetic radiation are transmitted from the earth station and these signals are received by the satellite.
The transponders in the satellite, retransmit it to different directions. These signals are then received by a large number of ground stations located in various regions. The signals received from the satellites are weak and are amplified before transmitting them. These are received by the television sets located far away from the program transmitting stations. Similar mechanism is followed for sending messages through other means of telecommunication like telephone, telex and FAX. For intercontinental telecommunication often two or three satellites are linked together.
