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We cannot doubt that the economic and social impact of these concepts will be very significant. Already, advanced systems of communication are affecting both the layman and the technician . Complex functions are being performed by people using advanced terminals which are intended to be as easy to use as the conventional telephone.
The new global satellite-communications systems will offer three kinds of service, which may overlap in many different kinds of receivers:
Voice. Satellite telephones will be able to make calls from anywhere on earth to anywhere else. That could make them especially useful to remote, third-world villages (some of which already use stationary satellite telephones), explorers and disaster-relief teams. Today’s mobile phones depend on earth-bound transmitters, whose technical standards vary from country to country. So business travelers cannot use their mobile phones on international trips. Satellite telephones would make that possible.
Massaging. Satellite messagers have the same global coverage as satellite telephones, but carry text alone, which could be useful for those with laptop computers. Equipped with a small screen like today’s pagers, satellite messagers will also receive short messages.
Tracking. Voice and messaging systems will also tell their users where they are to within a few hundred metres. Combined with the messaging service, the location service could help rescue teams to find stranded adventurers, the police to find stolen cars, exporters to follow the progress of cargoes, and haulage companies to check that drivers are not detouring to the pub. Satellite systems will provide better positioning information to anyone who has a receiver for their signals.
INTERNET
The internet, a global computer network which embraces millions of users all over the world, began in the United States in 1969 as a military experiment. It was designed to survive a nuclear war. Information sent over the Internet takes the shortest path available from one computer to another. Because of this, any two computers on the Internet will be able to stay in touch with each other as long as there is a single route between them. This technology is called packet swithing. Owing to this technology, if some computers on the network are knocked out (by a nuclear explosion, for example), information will just rout around them. One such packet-swithing network which has already survived a war is the Iraqi computer network which was not knocked out during the Gulf War.
Most of the Internet host computers (more than 50%) are in the United States, while the rest are located in more than 100 other countries. Although the number of host computers can be counted fairly accurately, nobody knows exactly how many people use the Internet, there are millions worldwide, and their number is growing by thousands each month.
The most popular Internet service is e-mail. Most of the people, who have access to the Internet, use the network only for sending and receiving e-mail messages. However, other popular services are available on the Internet: reading USENET News, using the World-Wide-Web, telnet, FTP, and Gopher.
In many developing countries the Internet may provide businessmen with a reliable alternative to the expensive and unreliable telecommunications systems of these countries. Commercial users can communicate cheaply over the Internet with the rest of the world. When they send e-mail messages, they only have to pay for phone calls to their local service providers, not for calls across their countries or around the world. But who actually pays for sending e-mail messages over the Internet long distances, around the world? The answer is very simple: users pay their service provider a monthly or hourly fee. Part of this fee goes toward its costs to connect to a larger service provider, and part of the fee received by the larger provider goes to cover its cost of running a worldwide network of wires and wireless stations.
But saving money is only the first step. If people see that they can make money from the Internet, commercial use of this network will drastically increase. For example, some western architecture companies and garment centers already transmit their basic designs and refined by skilled – but inexpensive – Chinese computer-aided-design specialists.
However, some problems remain. The most important is security. When you send an e-mail message can travel through many different networks and computers. The data is constantly being directed towards its destination by special computers called routers. However, because of this, it is possible to get into any of the computers along the route, intercept and even change the data being sent over the Internet. In spite of the fact that there are many good encoding programs available, nearly all the information being sent over the Internet is transmitted without any form of encoding, i.e. “in the clear”/ But when it becomes necessary to send important information over the network, these encoding programs may b useful. Some American banks and companies even conduct transactions over the Internet. However, there are still both commercial and technical problems which will take time to be resolved.
Реферат опубликован: 12/03/2008