The Public Switched Telephone Network
 

Lecture Notes: Session 2

TDC 461

  1. Announcements:
    1. Mail questions, info to HyperNews group
  2. Review
    1. List and describe the three major regulatory judgments affecting the telecommunications industry between 1900 and 1997.
    2. Discuss the trend toward wireless communications, giving industry examples.
    3. List four major advances in the telecommunications industry between 1990 and 1997 and explain why they are significant.
    4. The human voice produces an ___________ signal which, when converted to electrical energy is represented by a __________- wave, which is _________ in nature.
    5. The bandwidth required to support normal voice conversation is:
    6. Two techniques used to narrow the bandwidth of a channel are:

  3. The Public Switched Telephone Network
    1. Network=>Demarcation point (Demarc)=>also called station drop.
      Regulatory effect on network=>
    2. Pre-1984
    3.  

    4. Post-1984
  4. Topology of PSTN
    1. Star configuration from the Central Office (CO) to the demarc
      Star or ring configuration from the Central Office to other COs or higher-level offices
    2. Wire Center or Frame
    3. Switch=>
  5. Topology, Cont.
    1. Physical vs. logical connections
    2.  

    3. Facilities
  6. The Local Loop
    1. CO to customer demarc is called the Local Loop or Outside Plant
    2. Feeders: 50-3000 pairs of wire running from the CO in a general direction to manholes or handholds (splice points)
    3. Lateral distribution: bundles split off to run to branch feeders.
    4. Branch feeders: bundles split into four-pair groups and delivered to individual station drops.
  7. Network Hierarchy (pre-1984)
    1. Designed around the task of call completion.
  8. Class 5 Office: Local Exchange
  9.  

  10. Class 4 Office: Toll Center or Tandem Office
  11. Class 3 Office: Primary Center
  12.  

  13. Class 2 Office: Sectional Center
  14.  

  15. Class 1 Office: Regional Center
  16. Network Characteristics (post-1984)
    1. Bell Operating Companies (BOCs) become Local Exchange Carrier's (LECs)
    2. Original 7 BOCs become Regional Bell Operating Companies (RBOCs)
      1. Regulated arm
      2. Unregulated arm

     

  17. Equal Access
    1. Interexchange carrier (IEC or IXC) rights
    2. Removal of 7-10 digit additional codes for access to alternative long distance service
    3. Non-conforming end offices
  18. POPs and POIs
  19. POP=>point of presence
  20.  

  21. POI=>point of interface (no switch present)
  22. Numbering Plan for North America
    1. Area codes
    2.  

    3. Exchange codes
    4.  

    5. Subscriber Extensions

     

  23. Private Networks and Hybrid Networks
  24. Local Access and Transport Areas (LATAs)
    1. LATAs rationale
      1. 4 Types of LATA-based calls:
      2. Intrastate-IntraLATA=LEC
      3. Intrastate-InterLATA=IEC
      4. Interstate-InterLATA=IEC
      5. Interstate-IntraLATA=IEC or LEC
    2. Costing
  25. Telephone Handset
    1. contains four wires; 2 to transmit, 2 to receive
    2. Transmitter (mouth piece)
    3. Diaphragm->
    4. Receiver (ear piece)
    5. Handset cord and base
    6. Switchhook=>
    7. Tip and Ring=>
    8. Dial pad
    9. pulse=>
    10. tone=>
  26. Digital Phones
    1. completely programmable
    2. speed dial->
    3. call hold
    4. call transfer
    5. conference call
    6. redial last number
    7. power dialing
    8. speakerphone/hands-free dialing
    9. display dialing (caller ID)
  27. Transmission Model
  28. Big Concepts:
    1. Encode
    2. Transmit
      1. air is an atmospheric transmission medium
    3. Receive
      1. upon reception, signal is decoded
    4. Store
  29. Encoding
    1. Converting acoustical into electrical energy.
    2. Converting light energy into electrical energy.
    3. Converting light energy into latent chemical energy.
    4. Converting mechanical energy to electrical energy.
  30. Transmitting
  31. transmitting=>process of moving encoded information from one location to another
  32. Transmission: big concepts
    1. modulation
    2. amplification
    3. attenuation
    4. multiplexing
    5. duplexing
    6. frequency selection
    7. signal propagation
    8. signal conditioning
    9. switching
  33. modulation=>process of manipulating carrier signal to contain encoded information.
    1. Carrier signal=>constant signal that is sent during connection
    2. electromagnetic signals
    3. light signals
    4. What part of the signal gets changed?
    5. Methods of modulation
      1. Pulse Duration Modulation (PDM)=>telegraph
      2. Amplitude Modulation (AM)=>2400 cycle changes per second--baud
      3. Frequency Modulation (FM)
      4. Pulse Code Modulation (PCM)
  34. Amplification
    1. =>process of increasing carrier signal's strength.
  35. Attenuation
    1. =>loss of signal strength over time and distance
  36. Multiplexing
    1. =>process that enables optimal amounts of information to be moved over a communications channel
    2. Time Division Multiplexing (TDM)=>each encoding device is placed on the communications channel in a predetermined order, at a specific interval in time.--available on narrowband and broadband channels
    3. Frequency Division Multiplexing (FDM)=>Multiplexing device separates information from two or more devices and assigns each a particular frequency
      1. FDM is only available on "broadband" communications channels
      2. cable tv
  37. Duplexing
    1. =>manages/controls direction of information flow
  38. Simplex=>unidirectional; broadcast TV; telex
    1. Half duplex=>cb radio; can send and receive, but you can only do one at a time
  39. Full duplex=>send and receive simultaneously; telephone
  40. Frequency Selection
    1. 3 characteristics
    2. all are forms of radiant energy
    3. all have same velocity (~186,000 miles per second--same as light)
    4. all travel in a sine wave-like motion
  41. Bandwidth
    1. =>frequency range assigned to device capable of transmission by a physical or atmospheric channel
    2. Microwave
    3. Narrow-band
    4. Broadband
    5. Regulatory boards
      1. FCC
      2. International Telecommunications Union (ITU)
  42. Propagation
    1. =>the transporting or launching of a signal through a telecommunications channel
    2. Atmospheric channelling=>
      1. direct=>
      2. ground=>
      3. sky
    3. Physical channelling=>moving electrical, electromagnetic, and light energy through copper, glass (fiber) and wave guides
      1. open wire
      2. Copper Twisted Pair
        1. unshielded
        2. shielded
        3. 2-wire
        4. 4-wire
        5. cat 3
        6. cat 5
      3. coaxial cable
        1. =>used in VHF or lower spectrums
        2. composition
        3. ThinNet
        4. ThickNet
      4. Fiber optic
      5. composition
      6. repeaters vs. amplifiers (review)
      7. Wave Guide=>
        1. composition
        2. reality check
  43. Signal Conditioning
    1. =>process of converting encoded signal from one format to another
    2. application
    3. problems
    4. protocol converter
  44. Switching
    1. =>process that allows two or more communication devices to be connected.
      1. Sensing access request
      2. Determining destination
      3. Selecting path
      4. Establishing Connection
      5. Disconnecting the Circuit
  45. Receiving=>process of capturing an encoded signal and relaying it to the decoding device.
    1. Collecting=>
    2. Connecting=>
    3. Amplifying=>
    4. Demodulating=>
  46. Storing=>saving information (signals) for later use.
    1. Paper
    2. Film
    3. Magnetic Media
      1. Benefits
      2. Disadvantages
    4. Optical Disks
  47. Retrieving
    1. =>process of accessing stored information
    2. Abstracting=>process of identifying the content of stored information
    3. Indexing=>process of coding an item (name) for later retrieval
    4. Accessing=>process of locating a stored item by using the abstract and index
    5. Controlling=>determining who has access to specific information (also called authentication control)
  48. Decoding
    1. =>process of presenting information in a usable format.
    2. Converting electrical to acoustical energy
    3. Converting electrical to light energy
    4. Converting electrical to mechanical energy