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Computers (3)


Darbas anglų kalba. Channels of communication. Security and privacy on the Internet. Network configurations. WANs and worldwide communications. New technologies. Hackers!


What are ‘telecommunications’?
This term refers to the transmission of information over long distances using the telephone system, radio, TV satellite or computer links. Examples are two people speaking on the phone, a sales department sending a fax to a client or someone reading the teletext pages on TV But in the modern world, telecommunications mainly means transferring information from one PC to another via modem and phone lines (or fibre-optic cables).
What can you do with a modem?
A modem is your computer’s link to the external world. With a modem you can exchange e-mail and files with friends and colleagues; you can access the Web and search for information about the stock market, current affairs, entertainment, etc..; you can participate in newsgroups and live conversations; you can make bank transactions and buy things from the comfort of your home. You can also access your office from your computer at home or your laptop in a hotel room.
Your PC is a digital device (it works with strings of 1s and 0s). However, the telephone system is an analogue device, designed to transmit the sounds and tones of the human voice. That’s why we need a modem – a bridge between digital and analogue signals. The word ‘modem’ is an abbreviation of MOdulator/DEModulator. When a modem modulates, it sends very rapid on/off pulses. The computer on the other end translates (demodulates) those signals into intelligible text or graphics. Modem transmission speeds are measured in kilobits per second. Typical speeds on 28.8, 33.6 and 56 kbps.
Today a lot of companies find it more efficient to have some employees doing their work at home. Using a modem, they transfer their work into the office where it is printed and distributed. The list of applications is endless.
What do you need to telecommunicate?
You just need a PC (or a terminal), a modem 30 connected to the computer and the telephone line, and communication software. Once you have installed and configured your modem, you can communicate with people through bulletin boards and online services.
Local bulletin boards
Bulletin board systems (BBS) are frequently free because they are run by enthusiasts and sponsored by user groups or small businesses. The first time you make a BBS connection you are required to register your name, address, phone number and other information such as the kind of computer and modem you are using. The person who administers the BBS is called sysop (system operator). You can use a BBS to download artwork, games and programs, or you can participate in ongoing discussions. You can also upload (send) programs, but make sure they are shareware or public domain programs.
Online service providers
To gain access to the Internet you must first open an account with an Internet service provider (ISP) or a commercial online service provider. Both offer Internet access, but the latter provides exclusive services.
• Internet service providers usually offer access to the Web and newsgroups, an e-mail address, a program to download files from FTP sites, and IRC software so that you can have live chats with other users. Most ISPs charge a flat monthly or annual fee that gives you unlimited access to the Internet.
• The main commercial online services are America Online, CompuServe, Prodigy and Microsoft Network. They differ from dedicated ISPs in two ways: (1) they use a smooth, easy-to-use interface, and (2) they have extra services for members only (but they charge higher prices). For example, they offer airline reservations, professional forums, online shopping and stories for children. They also let you search their online encyclopaedias and special databases. ...

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Tinklalapyje paskelbta2006-11-28
DalykasKompiuterių referatas
KategorijaInformatika >  Kompiuteriai
Apimtis6 puslapiai 
Literatūros šaltiniai0
KalbaAnglų kalba
Dydis10.71 KB
Viso autoriaus darbų1 darbas
Metai2006 m
Švietimo institucijaAlytaus kolegija
Failo pavadinimasMicrosoft Word Computers (3) [speros.lt].doc

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