Telecommunications

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Telecommunications

• Tutorial

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Telecommunication

• is the transmission of signals over a distance
  for the purpose of communication.

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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).

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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.

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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.

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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.

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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.

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Internet Service Providers (ISP).

• ISP companies (exAOL, 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 companys 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 users computer connects through a modem that
  transfers the digital signal into a signal
  suitable for the transmission medium to the ISPs
  server.

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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.

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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.

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Web page addresses

• For example our school web pages 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)

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First Level Domain Addresses

• The .asp at the end of the URL is the school
  sites 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

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Domain Levels

• Each sequent domain level of the file farther
  identifies the site. Our schools 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.

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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.

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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.

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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.

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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.

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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.

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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
  engines database to look for matches or hits
  of the keyword(s) use in the web site.

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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.

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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.

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User Name

• The user name is located before the _at_ sign in
  the URL addresses. For example in the e-mail
  address
• someonesname_at_bcsemail.org
• someonesname is the username
• the _at_ symbol serves as the divider
• bcsemail.org is the server name.