Реферат: Untitled Essay Research Paper TelecommunicationsThe transmission of

Untitled Essay, Research Paper


The transmission of words, sounds, images, or data in the form of electronic or

electromagnetic signals or impulses. Transmission media include the telephone (using wire

or optical cable), radio, television, microwave, and satellite. Data communication, the

fastest growing field of telecommunication, is the process of transmitting data in digital

form by wire or radio.

Digital data can be generated directly in a 1/0 binary code by a computer or can be

produced from a voice or visual signal by a process called encoding. A data communications

network is created by interconnecting a large number of information sources so that data

can flow freely among them. The data may consist of a specific item of information, a

group of such items, or computer instructions. Examples include a news item, a bank

transaction, a mailing address, a letter, a book, a mailing list, a bank statement, or a

computer program.

The devices used can be computers, terminals (devices that transmit and receive

information), and peripheral equipment such as printers (see Computer; Office Systems).

The transmission line used can be a normal or a specially purchased telephone line called

a leased, or private, line (see Telephone). It can also take the form of a microwave or a

communications-satellite linkage, or some combination of any of these various systems.Hardware and SoftwareEach telecommunications device uses hardware, which connects a device to the transmission

line; and software, which makes it possible for a device to transmit information through

the line.Hardware

Hardware usually consists of a transmitter and a cable interface, or, if the telephone is

used as a transmission line, a modulator/demodulator, or modem.

A transmitter prepares information for transmission by converting it from a form that the

device uses (such as a clustered or parallel arrangement of electronic bits of

information) to a form that the transmission line uses (such as, usually, a serial

arrangement of electronic bits). Most transmitters are an integral element of the sending


A cable interface, as the name indicates, connects a device to a cable. It converts the

transmitted signals from the form required by the device to the form required by the

cable. Most cable interfaces are also an integral element of the sending device.

A modem converts digital signals to and from the modulated form required by the telephone

line to the demodulated form that the device itself requires. Modems transmit data through

a telephone line at various speeds, which are measured in bits per second (bps) or as

signals per second (baud). Modems can be either integral or external units. An external

unit must be connected by cable to the sending device. Most modems can dial a telephone

number or answer a telephone automatically.Software

Among the different kinds of software are file-transfer, host, and network programs.

File-transfer software is used to transmit a data file from one device to another. Host

software identifies a host computer as such and controls the flow of data among devices

connected to it. Network software allows devices in a computer network to transmit

information to one another.Applications

Three major categories of telecommunication applications can be discussed here:

host-terminal, file-transfer, and computer-network communications.Host-Terminal

In these types of communications, one computer—the host computer—is connected to

one or more terminals. Each terminal transmits data to or receives data from the host

computer. For example, many airlines have terminals that are located at the desks of

ticket agents and connected to a central, host computer. These terminals obtain flight

information from the host computer, which may be located hundreds of kilometers away from

the agent’s site.

The first terminals to be designed could transmit data only to or from such host

computers. Many terminals, however, can now perform other functions such as editing and

formatting data on the terminal screen or even running some computer programs.

Manufacturers label terminals as «dumb,» «smart,» or

«intelligent» according to their varying capabilities. These terms are not

strictly defined, however, and the same terminal might be labeled as dumb, smart, or

intelligent depending upon who is doing the labeling and for what purposes.File-Transfer

In file-transfer communications, two devices are connected: either two computers, two

terminals, or a computer and a terminal. One device then transmits an entire data or

program file to the other device. For example, a person who works at home might connect a

home computer to an office computer and then transmit a document stored on a diskette to

the office computer.

An outgrowth of file transfer is electronic mail. For example, an employee might write a

document such as a letter, memorandum, or report on a computer and then send the document

to another employee’s computer.Computer-NetworkIn computer-network communications, a group of devices is interconnected so that the

devices can communicate and share resources. For example, the branch-office computers of a

company might be interconnected so that they can route information to one another quickly.

A company’s computers might also be interconnected so that they can all share the same

hard disk.

The three kinds of computer networks are local area networks (LAN), private branch

exchange (PBX) networks, and wide-area networks (WAN). LANs interconnect devices with a

group of cables; the devices communicate at a high speed and must be in close proximity. A

PBX network interconnects devices with a telephone switching system; in this kind of

network, the devices must again be in close proximity. In wide-area networks, on the other

hand, the devices can be at great distances from one another; such networks usually

interconnect devices by means of telephone.Telecommunication ServicesPublic telecommunication services are a relatively recent development in

telecommunications. The four kinds of services are network, information-retrieval,

electronic-mail, and bulletin-board services.Network

A public network service leases time on a WAN, thereby providing terminals in other cities

with access to a host computer. Examples of such services include Telenet, Tymnet, Uninet,

and Datapac. These services sell the computing power of the host computer to users who

cannot or do not wish to invest in the purchase of such equipment.Information-RetrievalAn information-retrieval service leases time on a host computer to customers whose

terminals are used to retrieve data from the host. An example of this is CompuServe, whose

host computer is accessed by means of the public telephone system. This and other such

services provide general-purpose information on news, weather, sports, finances, and


Other information-retrieval services may be more specialized. For example, Dow Jones News

Retrieval Services provide general-purpose information on financial news and quotations,

corporate-earning estimates, company disclosures, weekly economic survey updates, and Wall

Street Journal highlights. Newsnet provides information from about 200 newsletters in 30

different industries; Dialog Information Services, BRS Bibliographic Retrieval Services,

and Orbit Information Retrieval Services provide library information; and Westlaw provides

legal information to its users. See Database.Electronic-Mail

By means of electronic mail, terminals transmit documents such as letters, reports, and

telexes to other computers or terminals. To gain access to these services, most terminals

use a public network. Source Mail (available through The Source) and EMAIL (available

through CompuServe) enable terminals to transmit documents to a host computer. The

documents can then be retrieved by other terminals. MCI Mail Service and the U.S. Postal

ECOM Service (also available through The Source) let terminals transmit documents to a

computer in another city. The service then prints the documents and delivers them as hard

copy. ITT Timetran, RCA Global Communications, and Western Union Easylink let terminals

send telexes to other cities.Bulletin-Board

By means of a bulletin board, terminals are able to facilitate exchanges and other

transactions. Many bulletin boards do not charge a fee for their services. Users of these

services simply exchange information on hobbies, buy and sell goods and services, and

exchange computer programs.Ongoing DevelopmentsCertain telecommunication methods have become standard in the telecommunications industry

as a whole, because if two devices use different standards they are unable to communicate

properly. Standards are developed in two ways: (1) the method is so widely used that it

comes to dominate; (2) the method is published by a standard-setting organization. The

most important organization in this respect is the International Telecommunication Union,

a specialized agency of the United Nations, and one of its operational entities, the

International Telegraph and Telephone Consultative Committee (CCITT). Other organizations

in the area of standards are the American National Standards Institute, the Institute of

Electrical Engineers, and the Electronic Industries Association. One of the goals of these

organizations is the full realization of the integrated services digital network (ISDN),

which is projected to be capable of transmitting through a variety of media and at very

high speeds both voice and nonvoice data around the world in digital form.

Other developments in the industry are aimed at increasing the speed at which data can be

transmitted. Improvements are being made continually in modems and in the communications

networks. Some public data networks support transmission of 56,000 bits per second (bps),

and modems for home use (see Microcomputer) are capable of as much as 28,800 bps.IntroductionWhen a handful of American scientists installed the first node of a new computer network

in the late 60’s, they could not know by any chance what phenomenon they had launched.

They were set a challenging task to develop and realise a completely new communication

system that would be either fully damage-resistant or at least functional even if an

essential part of it was in ruins, in case the Third World War started. The scientists did

what they had been asked to. By 1972 there were thirty-seven nodes already installed and

ARPANET (Advanced Research Projects Agency NET), as the system of the computer nodes was

named, was working (Sterling 1993). Since those «ancient times», during which

the network was used only for national academic and military purposes (Sterling 1993),

much of the character of the network has changed. Its today users work in both commercial

and non-commercial branches and not just in academic and governmental institutions. Nor is

the network only national: it has expanded to many countries around the world, the network

has become international and in that way it got its name. People call it Internet.The popularity of this new phenomenon is rising rapidly, almost beyond belief. In January

1994 there were an estimated 2 million computers linked to the Internet. However, this is

nothing compared to the number from last year’s statistics. At the end of 1995, 10 million

computers with 40-50 million users were assumed to be connected to the

network-of-networks. If it goes on like this, most personal computers will be wired to the

network at the end of this century (Internet Society 1996).The Internet is phenomenal in many ways. One of them is that it connects people from

different nations and cultures. The network enables them to communicate, exchange opinions

and gain information from one another. As each country has its own national language, in

order to communicate and make themselves understood in this multilingual environment the

huge number Internet users need to share a knowledge of one particular language, a

language that would function as a lingua franca. On the Internet, for various reasons, the

lingua franca is English.

Because of the large number of countries into which the Internet has spread and which

bring with

them a considerable variety of languages English, for its status of a global language, has

become a necessary communication medium on the Internet. What is more, the position of

English as the language of the network is strengthened by the explosive growth of the

computer web as great numbers of new users are connecting to it every day.Internet, in computer science, an open interconnection of networks that enables connected

computers to communicate directly. There is a global, public Internet and many

smaller-scale, controlled-access internets, known as enterprise internets. In early 1995

more than 50,000 networks and 5 million computers were connected via the Internet, with a

computer growth rate of about 9 percent per month.Services

The public Internet supports thousands of operational and experimental services.

Electronic mail (e-mail) allows a message to be sent from one computer to one or more

other computers. Internet e-mail standards have become the means of interconnecting most

of the world’s e-mail systems. E-mail can also be used to create collaborative groups

through the use of special e-mail accounts called reflectors, or exploders. Users with a

common interest join a mailing list, or alias, and this account automatically distributes

mail to all its members.

The World Wide Web allows users to create and use point-and-click hypermedia

presentations. These documents are linked across the Internet to form a vast repository of

information that can be browsed easily.

Gopher allows users to create and use computer file directories. This service is linked

across the Internet to allow other users to browse files.

File Transfer Protocol (FTP) allows users to transfer computer files easily between host

computers. This is still the primary use of the Internet, especially for software

distribution, and many public distribution sites exist.

The Usenet service allows users to distribute news messages automatically among thousands

of structured newsgroups. Telnet allows users to log in to another computer from a remote

location. Simple Network Management Protocol (SNMP) allows almost any Internet object to

be remotely monitored and controlled.Connection

Internets are constructed using many kinds of electronic transport media, including

optical fiber, telephone lines, satellite systems, and local area networks. They can

connect almost any kind of computer or operating system, and they are self-aware of their

capabilities. An internet is usually implemented using international standards

collectively called Transmission Control Protocol/Internet Protocol (TCP/IP). The

protocols are implemented in software running on the connected computer. Most computers

connected to the internet are called hosts. Computers that route data, or data packets, to

other computers are called routers. Networks and computers that are part of the global

Internet possess unique registered addresses and obtain access from Internet service


There are four ways to connect to the public Internet: by host, network, terminal, or

gateway access. Host access is usually done either with local area networks or with the

use of telephone lines and modems combined with Internet software on a personal computer.

Host access allows the attached computer to fully interact with any other attached

computer—limited only by the bandwidth of the connection and the capability of the


Network access is similar to host access, but it is usually done via a leased telephone

line that connects to a local or wide area network. All the attached computers can become

Internet hosts.

Terminal access is usually done via telephone lines and modems combined with

terminal-emulation software on a personal computer. It allows interaction with another

computer that is an Internet host.

Gateway access is similar to terminal access but is provided via on-line or similar

proprietary services, or other networks such as Bitnet, Fidonets, or UUCP nets that allow

users minimally to exchange e-mail with the Internet.Development

The Internet technology was developed principally by American computer scientist Vinton

Cerf in 1973 as part of a United States Department of Defense Advanced Research Projects

Agency (DARPA) project managed by American engineer Robert Kahn. In 1984 the development

of the technology and the running of the network were turned over to the private sector

and to government research and scientific agencies for further development.

Since its inception, the Internet has continued to grow rapidly. In early 1995, access was

available in 180 countries and there were more than 30 million users. It is expected that

100 million computers will be connected via the public Internet by 2000, and even more via

enterprise internets. The technology and the Internet have supported global collaboration

among people and organizations, information sharing, network innovations, and rapid

business transactions. The development of the World Wide Web is fueling the introduction

of new business tools and uses that may lead to billions of dollars worth of business

transactions on the Internet in the future.

In the Internet nowadays, the majority of computers are from the commercial sphere (Vrabec

1996). In fact, the commercialisation of the network, which has been taking place during

the last

three or four years, has caused the recent boom of the network, of the WWW service in


(Vrabec 1996). It all started in the network’s homeland in 1986, when ARPANET was


replaced by a newer and technologically better built network called NSFNET. This network


more open to private and commercial organisations (Vrabec 1996) which, realising the

potential of

the possible commercial use of the Internet, started to connect themselves to the network.There are several possibilities how commercial organisations can benefit from their

connection to

the English-speaking Internet. Internet users are supposed to be able to speak and


English, and actually most of them do. With the rapidly rising number of users, the

network is a

potential world market (Vrabec 1996) and English will be its important tool. The status of


as a world language, or rather its large number of people who are able to process and use

information in English, already enables commercial organisations to present themselves,

their work

and their products on the Internet. Thanks to English and the Internet companies can


with their partners abroad, respond to any question or give advice on any problem that


international customers can have with their products almost immediately (Vrabec 1996).

Considering the fact that many of the biggest, economically strongest and influential


are from the USA or other native English speaking countries, the commercialisation has

very much reinforced the use of English on the Internet.BIBLIOGRAPHY:Cepek, Ales and Vrabec, Vladimir 1995 Internet />CZ, Praha, Grada

Demel, Jiri 1995 Internet pro zacatecniky, Praha, NEKLAN

Falk, Bennett 1994 InternetROADMAP, translated by David Kr?sensk?, Praha, Computer


Jenkins, Simon 1995 «The Triumph Of English» The Times, May 1995

Philipson, Robert 1992 Linguistic imperialism, Oxford, Oxford University Press

Schmidt, Jan 1996 «Carka, hacek a WWW» Computer Echo Vol. 3/6

(also available on omicron.felk.cvut.cz/~comecho/ce/journal.html)

Sterling, Bruce 1993 «A short history of the Internet» The magazine Of Fantasy

And Science

Fiction, Feb. 1993

Vrabec, Vladimir 1996 «Komerce na Internetu» LanCom, Vol. 4/3

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