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Telecommunications Tutorial Telecommunication • is the transmission of signals over a distance for the purpose of communication. The basic elements of a telecommunication system • 1) A transmitter that takes information and converts it to a signal or code for transmission. a. The transmission may be a broadcast transmission that is sent to multiple receivers or a point-to-point transmission to a single receiver. • 2) A transmission medium over which the signal is transmitted. a. Common mediums are: free space, cable, and optical fiber. • 3) A receiver that converts the signal back to useable information. a. Some systems use transceivers which serve as both transmitter and receiver (ex. Telephone). Telecommunication Networks • The elements of a system may be linked with other systems to form a network of systems that communicate with each other. • Modern telecommunication systems use either an analogue or a digital signal. • Varying the modulation creates analogue signals. • Digital signals use a series of 1s and 0 s as a code. Telecommunication Networks • Private Networks: a group of two or more computer systems linked together which does not provide outside access. • Computers deliver Digital Information, the concept of meaning, knowledge, instruction, communication, representation, and mental stimulus through the Internet and other electronic resources, using digital code. Internet-The biggest computer network reaching millions of people on interconnected networks. • The Internet began in 1940 when George Stibitz transmitted problems from Dartmouth College in New Hampshire over teletype to his Complex Number Calculator in New York. • A four node network developed between UCLA, the Stanford Research Institute, the University of Utah and the University of California, Santa Barbara during the late 60s. • This network known as ARPANET had grown to 213 nodes by the early 80s. “LANs , WANs, and the WWW” • Local area networks (LANs) begin to develop. • Wide Area networks (WANs) consisting of two or more LANs connected by host computers formed covering wider geographical areas. • These early networks formed the World Wide Web (WWW) eventually allowing users access to text, graphics, sound and video. • There was no master plan or oversight, an Acceptable Use Policy (AUP) was developed by non-profit organizations as the WWW continued to grow. Internet Service Providers (ISP). • ISP companies (ex:AOL, Earthnet) offer connection to the Internet through servers and routers. Servers are powerful computers with large databases of internet addresses; routers are computers that direct the server to the quickest path to an internet site. • To connect to the ISP company’s server the user must have matching web browser software. The web browser gives the computer instructions about transforming data to protocol the server recognizes. • The user’s computer connects through a modem that transfers the digital signal into a signal suitable for the transmission medium to the ISPs server. Internet Protocol (IP): • Internet servers use IP addresses to identify individual computers web locations. • IP addresses are a series of numbers that are sequenced in a manner to identify locations by subdivisions, much as phone numbers and zip codes do. Domain Name System • The University of Wisconsin created the Domain Name System (DNS) in 1983. • The system links text names to IP addresses automatically. • Web addresses known as Uniform Resource Locators (URL) use specific text domain names that often give hints to the content of the site or e-mail address. Web page addresses • For example our school web page’s address is http://www.buncombe.k12.nc.us/ems/site/default.asp • URL addresses are divided into four sections: – The protocal (“http”) – The server name (“www”) – The file name (buncombe.k12.nc.us/ems/site/default), - First level domain names (.asp) First Level Domain Addresses • • • • • • The .asp at the end of the URL is the school site’s first level domain. First level domain addresses identify the type of site being located, they include: .asp - application software provider .com- commercial sites .org- organizations .net- networks .edu- education (primarily used by universities) .gov- government Domain Levels Each sequent domain level of the file farther identifies the site. Our school’s site http://www.buncombe.k12.nc.us/ems/site/default.asp has: • .us (United States) • .NC (North Carolina), • .buncombe • /ems (Enka Middle School) among its domain levels to help identify the site. Web-sites • Websites begin with a homepage, which not only introduces the site but also uses links to jump to other pages within the site when clicked. • Hyperlinks and hypertext take the user to related information in other sites. • The navigation of a site may use button bars or other graphics which are highlighted in a different color than the other text and graphic borders to help identify the link. • A small hand appears on the screen when the pointer is over a link. Types of Web-sites • Blog, short for Web log, is a webpage that serves as a publicly accessible personal journal for an individual. Typically updated daily, they often reflect the personality of the author. • Threaded Discussion is a set of related messages in an online group or e-mail. One of these includes the initial message and all replies to that message. Types of Web-sites • Bulletin boards: sites on which online discussion groups participate in forums, an exchange of open messages with participants with common interests. Internet/ Web-Site Features • Computers may have filters using content control software to screen content from web-sites. • Bookmarks/Favorites allows the computer to form a list of URL addresses for often used web sites. The sites may be opened with a click without typing in URL addresses • File Transfer Protocol allows the exchange of files over the internet. Internet/ Web-Site Features • Data streaming a technique for transferring data such that it can be processed as a steady and continuous flow. Data streaming allows web sites to show short video clips. • WYSIWYG, pronounced “wizzy wig”, is an acronym for “What You See Is What You Get”. A feature which allows text and graphics shown by a website to exactly match a printout of the page. Search Engines • Search engines are large databases of web site URLs. • Commercial Search Engines such as Google and Yahoo were developed to help navigate the Web. • Users of search engines use search strategies to locate pertinent information. – Try to guess the URL. – Use subject directories provided by the search engine. – Use keyword search provided by the search engine’s database to look for matches or “hits” of the keyword(s) use in the web site. E-mail (electronic mail): • Has become one of the most widely used types of communication. • E-Mail is used by individuals or companies to communicate written messages to other individuals or companies. • Unsolicited e-mail or Spam is used in mass mailings to advertise products or causes. Often referred to as junk mail it can clog e-mail accounts. E-Mail • E-mail addresses use URL addresses with domain name levels to locate the e-mail server. The email server has a list of user names to which it routes incoming e-mail messages. User Name The user name is located before the @ sign in the URL addresses. For example in the e-mail address: [email protected] • someonesname is the username • the @ symbol serves as the divider • bcsemail.org is the server name.