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Communication systems.

Communication system is a type of systems, by which information is passed between two or more figures. In this text I will consider the most popular channels of communications. So, let us start with the most significant term revealed to communication systems. What are the telecommunications?

Telecommunications refers to the transmission of signals over a distance for the purpose of communication. Information is transmitted by devices such as the telephone, radio, television, satellite, or computer networks. Examples could be two people speaking on their mobile phone, a sales department sending a fax to a client, or even someone reading the teletext pages on TV. But in the modern world, telecommunications mainly means transferring information across the Internet, via modem, phone lines or wireless networks.

Because of telecommunications, people can now work at home and communicate with their office by computer and telephone. This is called teleworking. It has been predicted that about one third of all work could eventually be performed outside the workplace. In call centers, assistance or support is given to customers using the telephone, email or online chats. They are also used for telemarketing, the process of selling goods and services over the phone.

Digital TV and radio

In recent years, TV and radio broadcasting has been revolutionized by developments in satellite and digital transmission. Digital TV is a way of transmitting pictures by means of digital signals, in contrast to the analogue signals used by traditional TV. Digital TV offers interactive services and pay multimedia - that is, it can transmit movies and shows to TV sets or PCs on a pay-per-view basis. It is also widescreen, meaning programs are broadcast in a native 16:9 format instead of the old 4:3 format. Digital TV provides a better quality of picture and sound and allows broadcasters to deliver more channels.

Digital Terrestrial TV is received via a set-top-box, a device that decodes the signal received through the aerial. New technologies are being devised to allow you to watch TV on your mobile. For example, DMB (Digital Multimedia Broadcasting) and DVB-H (Digital Video Broadcast-Handheld) can send multimedia (radio, TV and data) to mobile devices.

Audio programs (music, news, sports, etc.) are also transmitted in a digital radio format called DAB (Digital Audio Broadcasting).

Mobile communications

Thanks to wireless connectivity, mobile phones and BlackBerrys now let you check your email, browse the Web and connect with home or company intranets, all without wires.

The use of GPS in cars and PDAs is widespread, so you can easily navigate in a foreign city or find the nearest petrol station.

Another trend is wearable computers. Can you imagine wearing a PC on your belt and getting email on your sunglasses? Some devices are equipped with a wireless modem, a keypad and a small screen; others are activated by voice. The users of wearable technology are sometimes even called cyborgs' The term was invented by Manfred Clynes and Nathan Kline in 1960 to describe cybernetic organisms - beings that are part robot, part human.



Characteristics of Communication Systems

· Must be a Sender and Receiver

· A protocol is a set of rules which governs the transfer of data between computers. Protocols allow communication between computers and networks.

· Handshaking is used to establish which protocols to use. Handshaking controls the flow of data between computers

· protocols will determine the speed of transmission, error checking method, size of bytes, and whether synchronous or asynchronous

· Examples of protocols are: token ring, CSMA/CD, X.25, TCP/IP
Computing problems

Every communication system has 5 basic requirements

• Data Source (where the data originates)

• Transmitter (device used to transmit data)

• Transmission Medium (cables or non cable)

• Receiver (device used to receive data)

• Destination (where the data will be placed)

Web design

A website is a set of related web pages served from a single web domain. The code behind most web pages is HTML, which consist of commands called tags. Tags are placed around pieces of text to tell the web browser how to display text or pictures. You needn’t learn HTML in order to build your own website. Instead, you can use a word processor with web design capabilities or a dedicated web editor like Macromedia Dreamweaver. Wed editors are user friendly. You can draw how will look your web page and get it’s the source code – different buttons and menu items let you design a page without writing HTML. There are a number of different elements that you can use on a web page: text, background, tables, frames, Cascading Style Sheets, graphics, hyperlinks.

And now little more about every of this items. Text displayed in variety of fonts and sizes. Most text files are available in two formats: HTML or PDF. Background - the underlying colors and patterns of a web page. Tables with columns and rows, used to position images and text on a page. Frame is a rectangular area that allows the display of different pages in the same browser window. CSS is a mechanism for adding styles to web documents.

Many websites incorporate audio and video files, if you’re designing a site, you may like to insert songs, podcasts etc. The most common audio formats are: .wav, .ra, .mp3. Full-motion video is stored in these formats: .avi, .mov, .mpg. If you want to inject something special into your web pages, you can use Adobe Flash to include interactive animations and streaming audio. Additionally, you can insert Java applets - small programs that enable the creation of interactive files. Animations are made up of a series of idependent pictures put together in sequence to look like moving pictures. To see or hear all these files, you must have the right plug-in, an auxiliary program that expands the capabilities of your web browser.


Date: 2016-01-14; view: 2565


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