Lesson 7 data communication


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Lesson 7 data communication

  2. 2. High speed data exchange between computers and/or other electronic devices via cable or wireless.
  3. 3. A code developed by Samuel Morse used for transmitting messages in which letters of the alphabet and numbers are represented by various sequences of written dots and dashes, or short and long signals such as electric tones or voltages. Morse code was used extensively in telegraphy. In a format that has been standardized for international use, it is still sometimes used for long distance radio communication.
  4. 4.  By 1851, more than fifty telegraph companies were in operation. In 1874, a Frenchman Emile Baudot invented a telegraph multiplexer and developed a code suitable for machine encoding and decoding.
  5. 5.  In1876 telephone was invented by Dr. Alexander Graham Bell. Founder of the Bell Telephone Company by the year of 1877.
  6. 6.  (Universal Automatic Comp uter) The first commercially successful computer, introduced in 1951 by Remington Rand. Over 40 systems were sold. Its memory was made of mercury-filled acoustic delay lines that held 1,000 12-digit numbers. It used magnetic tapes that stored 1MB of data at a density of 128 cpi.
  7. 7. A medium through which a message is transmitted to its intended audience, such as print media or broadcast (electronic) media.
  8. 8.  A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the UTP CAT. 5E network. Other types of cables used for LANs include coaxial cables and fiber optic cables.
  9. 9.  Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet. Although more expensive than standard telephone wire, it is much less susceptible to interference and can carry much more data. COAXIAL CABLE
  10. 10.  Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In FIBER-OPTIC CABLE the future, almost all communications will employ fiber optics
  11. 11.  Microwave communication is the transmission of signals via radio using a series of microwave towers. Microwave communication is known as a form of "line of sight" communication, because there must be nothing obstructing the transmission of data between these towers for MICROWAVE DATA signals to be properly sent TRANSMISSION and received.
  12. 12.  Satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth. There are hundreds of satellites currently in operation. They are used for such diverse purposes as weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global SATELLITES Positioning System, (GPS).
  13. 13. In telecommunications, data transfer is usuallymeasured in bits per second. For example, a typical low-speed connection to the Internet may be 33.6 kilobits per second (Kbps). On Ethernet local area networks, data transfer can be as fast as 10 megabits per second. Network switches areplanned that will transfer data in the terabit range.
  14. 14. Bandwidth describes the maximum data transfer rateof a network or Internet connection. It measures howmuch data can be sent over a specific connection in a given amount of time.
  15. 15. Baseband refers to the original frequency range of a transmission signal before it is converted, or modulated, to a different frequency range.
  16. 16. refers to high-speed data transmission in which a single cable can carry a large amount of data at once. The most common types of Internet broadband connections are cable modems (which use the same connection as cable TV) and DSL modems (which use your existing phone line). Because of its multiple channel capacity, broadband has started to replace baseband, the single-channel technology originally used in most computer networks.
  17. 17.  The word modem is actually short for Modulator/Demodulator. A modem is a communications device that can be either internal or external to your computer. It allows one computer to connect another computer and transfer data over telephone lines. The original dial-up modems are becoming obsolete because of their slow speeds and are being replaced by the much faster cable INTERNET MODEM and DSL modems.
  18. 18.  An external modem is a box that attaches to a computers COM port via cables. EXTERNAL MODEM
  19. 19.  A modem that resides on an expansion board that plugs into a computer. INTERNAL MODEM
  20. 20.  A device you can attach to a personal computer that enables you to transmit and receive electronic documents as faxes. A fax modem is like a regular modem except that it is designed to transmit documents to a fax machine or to another fax modem. Some, but not all, fax modems do double duty as regular modems. As with regular modems, fax modems can be either internal or external. Internal fax modems FAX MODEM are often called fax boards.
  21. 21. Multiplexer is a device that selects one ofseveral analog or digital input signals and forwards the selected input into a single line.
  22. 22. A type of multiplexor that combines multiple channels onto a single transmission medium in such a way that all the individual channels can be simultaneously active.
  23. 23. This processor is a computer that handles communications processing for a mainframe by connecting to thecommunications lines on one end and the mainframe on the other. It transmits and receives messages, assembles and disassembles packets, and detects and corrects errors. Sometimes it is synonymous with a communications controller, although the latter is usually not as flexible.