* The figure show the basic operation of a communication satellite.
An earth station transmit information to the satellite.The satellite contains a
receiver which picks up the transmitted signal,amplefiers it, and translates it to
another frequency.This new frequency is then retransmitted to the receiving stations
back on earth.The original signal being transmitted from the earth station to the
satellite is called the uplink, and retransmitted signal from the satellite to the
receiving station is called the downlink.Usually the downlink frequency is lower than
the uplink frequency.The transmitter receiver combination in the satellite is known
as a TRANSPONDER.