Transcript Telecommunications

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
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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.