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Telecommunications

Telecommunications. "This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us.” Western Union internal memo, 1876. . Some Applications. Electronic mail Electronic commerce Sharing/distribution of information

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Telecommunications

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  1. Telecommunications "This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us.” Western Union internal memo, 1876.

  2. Some Applications • Electronic mail • Electronic commerce • Sharing/distribution of information • Telecommuting • Distance learning (our mission) • “Getting out of the box”

  3. Basic Telecommunications Architectures • Where is the “intelligence”? • Centralized • Distributed • Hybrid

  4. Terminal Terminal Terminal Terminal Centralized Architecture • The earliest • Central mainframe or minicomputer • “Dumb” terminal • Awful user interface • Lots of control • Not easily scalable Mainframe

  5. Centralized Architecture

  6. PC PC PC PC Distributed Architecture • Intelligence on the desktop • Local area network • “Extra disk drive” • Less costly • More user-friedly • More easily scalable • Less capacity for OLTP • Multiple vendors File Server

  7. Client Client Client Client Hybrid Architecture • The latest and most exciting • Mixture of processing tasks • Central machine as “server” • Desktop machines as “clients” Data Server

  8. Communications Modes and Codes • Analog vs. digital • Data codes • Asynchronous vs synchronous • Simplex, etc. • Circuit switching vs. packet switching • Media

  9. Modes and Codes (cont.) • Analog vs. digital • Why do you need a modem from home? • Data codes • ASCII • EBCDIC

  10. Modes and Codes (cont.) • Asynchronous signal - not related to time (generally less sophisticated) • Synchronous - used for high-speed data communications

  11. Modes and Codes (cont.) • Simplex, etc. • Simplex - one way transmission • Half-duplex - two way, but not simultaneously • Full-duplex - two way, simultaneously

  12. Modes and Codes (cont.) • Circuit vs. packet switching • Dedicated circuit (phone system) • Packets used in data communications

  13. Modes and Codes (cont.) • Media • Twisted pair • Coaxial cable • Fiberoptic cable • Over the air

  14. Modes and Codes (cont.) • The electromagnetic spectrum • Electromagnetic energy • “The force” • Wireless communications • Nature of energy changes with frequency

  15. The Electromagnetic Spectrum Source: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/graphics/spectrum.gif

  16. Recent Enhancements

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