Communicate between distant locations.
i dont know please help me !!
Mostly a historic artifact. When AT&T controlled the industry and use devices like Strowger Switches, other electromechanical devices and large battery backup system it was likely the best tradeoff decided on by the engineers.
There are lots of satellite manufacturers all over the world. The most important ones (of geosynchronous satellites) are Thales Alenia Space (from Italy and France), JSC Information Satellite Systems (in Russia), Boeing (USA), Astrium (a European consortium in France, Germany, Spain, and UK), Lockheed Martin (USA), and Space Systems / Loral (USA). Among satellite platform manufacturers (listing is far from complete) are Amsat (international consortium USA, Canada, etc.), Ball Aerospace (USA), British Aerospace (UK), Fairchild (USA), Fokker (Netherlands), General Electric (USA), Hawker Siddeley (UK), Hughes (USA), IHI (Japan), Khrunichev (Russia), Mitsubishi (Japan), Northrop (USA), Philco Ford (USA), Rockwell (USA), RKK Energiya (Russia), SPAR Aerospace (Canada), Surrey Satellite (UK), Yuzhnoye (Ukraine). Launch vehicles (rockets in non-technical language; listing not complete) are from Arianespace (Europe), EADS (Europe), ISC Kosmotras (Russia) Space Quest (USA), Space X (USA), Starsem (Europe), United Launch Alliance (USA), Yuzhmash (Ukraine). The satellites are owned by the various space agencies, international organizations (e.g. Eumetsat) or private operators (telecommuncation agencies).