12. Ответьте на вопросы:

1. What type of connection is used by the phone system?

2. What does the phone company do?

3. What is a multipoint configuration?

4. What does the equipment aboard the satellite do?

14. Прочтите и переведите текст:

TEXT C

COMMUNICATIONS NETWORKS

A communications network links computers and computing devices so they can share information, yet continues to operate independently. Such networks can link microcomputers, terminals, minicomputers, mainframe computers, and computing devices such as printers and storage devices. Networks have grown rapidly in popularity because they give users access to computers and devices beyond the computer they are currently using.

Local-Area Networks. Local area networks (LANs) are used to connect computers and computing devices that are located in the same general area: in the office, in one building, or in one group of buildings in the same organization. Examples include microcomputers connected together in a college lab, microcomputers in a sales office and several different buildings that are connected to the organization’s mainframe computer located in the basement of one of the buildings.

Wide-Area Networks. Wide-area networks (WANs) are used to connect computers and computing devices that are separated by greater distances. An example would be an inventory-management network that ties together groups of microcomputers in local sale offices in many different cities. These local networks may in turn be interconnected with a set of company mainframes and minicomputers that are located at the company headquarters in yet another city.

Additionally, networks are often categorized as either baseband or broadband. The difference lies in the speed of communications between stations on the network. Baseband networks are the slower of the two, usually using twisted-pair wire connections. Broadband networks use higher-speed and multiple-channel.

Network Nodes. A network may include a variety of computers (micros, minis, and mainframes) and computing devices such as printers, storage devices, and digitizers. Either a computer or a computing device can occupy a node on the network. In some cases, a peripheral device such as a printer may be attached to one computer on the network; nevertheless, the device can often still be accessed by other computers on the network.

Cabling. Each of the computers and computing devices that are attached to the network must be physically connected or connected through broadcasting and receiving devices. The wiring of a network can vary considerably. The data-transmission capabilities of the cabling are usually dictated by the complexity of the network and the distance between stations. Complex, widespread networks often use more expensive, faster cabling media.

Network Interface. To enable interconnections between computers on the network, each computer must include an interface device. The cabling is connected directly to the physical port that is provided by the interface device. These interface hardware components may be built into a computer, or they may be provided by a specialty manufacturer and added to the computer.

Server. Computers and computing devices on a network may be connected to a server. A server (also known as a file server) provides a data storage function for the entire network. Often, a microcomputer is used to provide this server function, and it may also provide other network functions.

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