TELECOMMUNICATIONS AND NETWORKS

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CHAPTER 4

• TELECOMMUNICATIONSAND NETWORKS

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Basic Definitions

• Telecommunications the electronic transmission
  of signals for communications
• Telecommunications medium anything that carries
  an electronic signal and interfaces between a
  sending device and a receiving device

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The Components of Telecommunications Systems

• Hardware
• Sending/receiving unit
• Computers, Telephones, Fax, Radio sets, TV sets
• Telecommunications devices
• Telecommunications media
• Telecommunications network

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The Components of Telecommunications Systems
(cont)

• Communications software
• Communications protocols
• Communications applications
• E-mail
• Facsimile
• EDI, EFT.
• Communications provider

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The Components of Telecommunications Systems
Telecommunications Device
Telecommunications Device
Receiving Unit
Sending Unit
Communications Channels and Media
Receiver
Transmitter
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Data and Signals

• Data
• Raw facts
• Static
• Signals
• Transmit data
• Dynamic
• Data and signals may be digital or analog

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Digital and Analog Data

• Analog data is represented as continuous waveform
• Example audio tape
• Digital data is computer data sequence of
  binary 0s and 1s
• Example data stored on the hard drive

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Analog vs. digital signals
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Signals

• Analog signals
• Amplitude height of wave above or below a
  reference point
• Frequency a number of oscillations per time
  unit
• Phase determines the shift in time when wave
  obtains maximal value
• Digital signals
• Baud rate

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Data Transmission

• Digital data using digital signals
• Encoding
• Digital data using analog signals
• Modulation
• Analog data using digital signals
• Pulse code modulation
• Analog data using analog signals
• AM, FM radio, broadcast television

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Telecommunications Devices

• Modem
• an analog network is used to transmit digital
  data
• Fax modem
• Transmits images via standard telephone line
• Multiplexer
• an electronic device that allows a single
  communications channel to carry data transmitted
  simultaneously from many sources
• Private Branch Exchange
• a private telephone network used within an
  organization. Users of the PBX share a certain
  number of outside lines for making telephone
  calls external to the PBX.

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Telecommunications Devices (cont)

• Front-end processor special purpose computer
  that managers communication
• Switch receives a message and forwards it to one
  of the output ports to reach another device on
  the same network
• Bridge connects networks with the same
  transmission protocol
• Router connects dissimilar networks and forwards
  packets to intended destinations
• Gateway a network device which interfaces two
  different networks and implements required
  translations and conversions.

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Media for Data Transmission

• Guided transmission (cable) media
• Twisted-pair wire
• Coaxial cable
• baseband transmission a single signal is used
• broadband transmission available medium is
  divided into multiple channels.
• Fiber optic cable
• Wireless transmitting

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Wireless Media (continued )

• Microwave transmission
• Terrestrial microwave
• Satellite
• Geostationary earth orbit (GEO) - 22,300 miles
• Medium earth orbit (MEO) - 6,000 miles
• Low earth obit (LEO) - 400 to 1,000 miles
• Radio
• High bandwidth

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Wireless Media (continued )

• Cellular radio technology
• transfers calls from one cell to another
• Mobile computing
• occurs on radio-based networks that transmit data
  to and from mobile computers
• Infrared
• commonly used in remote control units

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Networks

• Personal Area Networks interconnect IT devices
  within 33 feet
• Local Area Networks connect two or more
  communications devices within 2,000 feet
• Metropolitan Area Networks are networks that
  serve an area of 3 to 30 miles
• Wide Area Networks large networks that serve
  large geographical regions

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Computer Networks

• Computer network computers and the
  communications media, devices, and software
  needed to connect two or more computer systems or
  devices
• Network nodes the computers and/or devices on
  the networks

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Network Communications Software

• Functions
• Message formatting
• Error checking
• Communications log
• Data security
• Translation
• Main groups
• Network Operating Systems
• Protocols
• Network Management Software

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Protocols

• NOS refers to a protocol to implement data
  transmission
• Protocol set of rules for data exchange
• Main conceptual components
• Syntax
• Semantics
• Timing

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Types of Data Processing in Organizations

• Centralized processing all processing occurs in
  a single location or facility
• Decentralized processing processing devices are
  placed at various remote locations
• Distributed processing computers are placed at
  remote locations but connected to each other via
  a network

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Types of Distributed Data Processing in the
Organizations

• Client a computer requesting a service
• Server a computer providing the service
• Client/Server Architecture and Processing
• Remote procedure call