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Lesson 1 the pstn

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Lesson 1 the pstn

  1. 1. Lesson 1 Topics PSTN Overview The Role of The PSTN CPE – An Example, How A Telephone Works Lesson 1 Topics PSTN Overview The Role of The PSTN CPE – An Example, How A Telephone Works Public Switch Telephone NetworkPublic Switch Telephone Network Thought For The Week Building on Lessons Learned In TCM 134 TheThe
  2. 2. Study This Set Of PowerPoint Slides Complete Assignment 1 And Post All Answers In The Lesson 1 Drop Box By The Due Date.
  3. 3. In This Lesson, You Will Learn How The Public Switch Telephone Network (PSTN) Was Originally Designed To Carry Voice Services. Next, We Will Learn That The Original Design Of The PSTN Has Evolved To Carry Most Of Today’s Advanced Voice, Data And Video Services. You Will Study A Brief Overview Of The PSTN – A Building Block For Our Course. Finally, You Will Learn How One Piece Of CPE Works In Conjunction With The PSTN. Objectives
  4. 4. Section 1.1 – PSTN Overview
  5. 5. The Public Switch Telephone Network (PSTN) Is A Mesh Network Of Lines, Trunks, Switches, Etc. That Connects Customer Provided Equipment (CPE) Together To Allow The CPE To Communicate Together. The PSTN Was Originally Designed To Optimize The Transmission Of Voice Services. What Is The PSTN?
  6. 6. Major Elements Of The PSTN CO Class 5 Switch CO Class 2 Switch Residence CPE CO Class 1 Switch PBX or KTS Digital LoopAnalog Loop Digital Interoffice Trunks Office Bldg PSTN
  7. 7. There Are Four Major Elements Of Today’s Public Switched Telephone Network (PSTN). Customer Premises Equipment (CPE) Access System Transport Signaling The Four Major Elements Of The PSTN
  8. 8. Prior To 1984 And The Breakup Of The AT&T Monopoly, All Parts Of The Public Switched Telephone Network Was Owned And Operated By The Telephone Company. After 1984, The Ownership And Maintenance Of All Telecommunications Equipment And Wiring On The Customer’s Site Became The Responsibility Of The Customer. Customer Premises Equipment
  9. 9. Customer Premises Equipment Includes:Customer Premises Equipment Includes: Telephones Fax Machines Wiring & Jacks Multiplexers Cross Connect Systems Computers PBXs Key Systems CSUs DSUs Video Codecs Etc.
  10. 10. Customer Premises Equipment - Continued:Customer Premises Equipment - Continued: Each Of These Pieces Of CPE Are Different. They Each Work Differently Electronically, And Many Have Different Ways In Which They Connect To The PSTN. Later In This Lesson We Will Study In More Detail, As One CPE Example, How Telephones Work Electronically And How They Connect To The PSTN. Later In This Course, We Will Study How Several Other CPEs Work Electronically And How They Connect To The PSTN.
  11. 11. The FCC Defined A Point, The Demarcation Point, In The Telecommunications Network That Separates CPE From Telephone Company-Provided Equipment And Wiring. The Demarcation Point Is Often Referred To As The Demarc. Demarcation Point
  12. 12. The Access Component Of The PSTN Provides Customers All Of The Wiring And Equipment For The Customer’s CPE To Be Connected To The Central Core Of The Public Switched Telephone Network. The Access System Includes Both Lines And Trunks And The Termination Equipment In The End Office. Access Lines And Trunks Along With The Telephone Poles, Conduits, Connector Boxes, Etc. Are Referred To As The Local Loop. Access System
  13. 13. Some Samples Of End Office Termination Equipment. Central Office Termination Equipment
  14. 14. Most Access Circuits Run From The Carrier’s Central Office And A Residence Are Analog Circuits (Ref. Slide 6). Most Access Circuits Run Between The Carrier’s Central Central Office And Businesses With Private Branch Exchanges Are Digital Circuits (Ref. Slide 6). Since Most Circuits That Connect Central Offices To Customer Premises Are Connected To Residences, Then, Most Circuits In The Local Loop Are Analog. Access System
  15. 15. Access System – Residential Access Class 5 Switch Each Customer Circuit Is A Two-Wire Cable From The Customer Demarc Out To The First Cross Connection Box A & B – Cross Connection Pedestal Or Cross Connection Box
  16. 16. Access System – Residential Access Class 5 Switch Even Though Customer Circuits Are Two-Wire Cable, Carriers Will Install Either 2-Pair, Or 4-Pair Cable. Customer Circuits Are Combined With Other Circuits At The Cross Connection Box 2-Pair Cable 100-Pair Cable
  17. 17. Access System – Residential Access Class 5 Switch Each Customer Circuit Is A Two-Wire Cable From The Customer Demarc Out To The First Cross Connection Box. From The Cross Connection Box To The Central Office The Customer Two-Wire Circuit Is Carried Inside Of A Much Thicker Cable That Carries 100 Pairs Of Cable Or More. Each Customer’s Two-Wire Circuits Remain Separate From Other Customer’s Circuits Which Are Carried On Separate Sets Of Wires.
  18. 18. Plastic Insulator Metal Conductor Sample 4-Pair Cable The Photo Below Shows A 4-Pair Copper Wire Cable Similar To The Type Of Cable That Might Be Run To A Residence. Each Pair Of Cable Supports A Separate Circuit. Because Of The Cost Of Installing Outside Cable, Carriers Usually Install More Than 1 Pair Of Wires.
  19. 19. Access System – Business Access Class 5 Switch Access For Small Business Customer Circuits Are Similar To Residential Access Circuits. Business Trunks From PBXs Are Digital, Usually T1s Or T3s. If The Trunks Are T1s, 24 Separate End-User Applications Are Carried On One Set Of Wires At A Time. We’ll Study More About Data Rates Of Trunks In The Lessons In Module 3 Of Our Text. Trunks Business W/ PBX
  20. 20. Transport Component Of The PSTN Transport Means Transmission – Taking Voice, Data, And Video Signals From One Subscriber’s Access Line And Delivering Them To Another Customer’s Access Line. The End-Office, Or Class 5 Central Office Is The Point Where All Customer Access Lines Connect. The Trunks Within The Transport Core Include A Wide Variety Of Transmission Speeds (e.g. T1, T3, OC-1, OC-12) And Transmission Media (e.g. Copper And Optical Fiber). We’ll Study More About The Transport System Later In This Course.
  21. 21. Signaling Component Of The PSTN Signaling Means The Controlling Of Calling Including: Setting Up A Path For A Conversation Through The Transport Core. Maintaining And Terminating The Conversation Path. Collecting Billing Information. Handling Other Supervisory Functions. We’ll Study More About The Signaling System Later In This Course.
  22. 22. Section 1.2 – The Role Of The PSTN
  23. 23. Many People View Voice Services, And The PSTN Used To Deliver Those Services, As “Old, Ho- Hum” Topics. Those People Reason That The Most Lucrative, Future Growth Areas In Telecommunications Will Be In Data Services As Opposed To Voice Services. Many Of Those People Believe That Telecommunications Students Should Not Study Topics Related To Voice Communications Services And The PSTN. The Role Of The PSTN
  24. 24. Those Same People Believe That Data Communications Will Underpin The New Emerging Technologies And Will Be The “Wave Of The Future”. Why Then Study Plain Old Telephony? The Role Of The PSTN - Continued
  25. 25. Throughout This Course We Will Learn How POTS And The PSTN Play Vital Roles In Providing Many Services Such As: Voice-over-IP (VoIP) Third Generation Cellular Internet Applications E-Mail E-Commerce WANs & MANs Etc., Etc., Etc. Today’s Emerging Technologies Do These Services Seem Like POTS!
  26. 26. Cellular – Many Major Cellular Features Depend On The PSTN – Two Examples Follow Several Examples Of The Role Of The PSTN
  27. 27. A Cell Call Placed To A Land-Based Phone Travels Through The PSTN CO Class 5 Switch CO Class 2 Switch CO Class 1 Switch Analog Loop Digital Interoffice Trunks Radio Controller MTSO Cellular User Residence CPE
  28. 28. InternetSS7/ PSTN Cellular Roaming Depends On The PSTN SS7 Network Roaming MTSO Home MTSO VLR HLR SSP SSP STP STP Roaming Cellular User Cellular Roaming Would Not Be Possible Without SS7 Network In PSTN
  29. 29. Private Line Data Networks Rely On Several Elements Of The PSTN Another Example Of The Role Of The PSTN
  30. 30. Site A Site B 56 Kbps Private Line Site E 56 Kbps Private Line T3 Private Line Site D OC3 Private Line Site C 56 Kbps Private LineT1 Private Line PSTN Backbone Circuits Are Provisioned To Create Corporate Private-Line Data Networks Router Router Router Router Router
  31. 31. Internet Access Relies On The PSTN – Another Example
  32. 32. ISP Access Use PSTN Circuits CO Class 5 Switch CO Class 2 Switch CO Class 1 Switch Multiplexed/Channelized Digital Loop Analog Loop Digital Interoffice Trunks Residential End-User ISP MCDL Corporate End-User PSTN Router
  33. 33. Section 1.3 – Customer Premises Equipment
  34. 34. CPE Includes All Telecommunications-Related Equipment That Is Located On The Consumer’s Side of the Demarcation Point. Customer Premises Equipment Customer Premises EquipmentCustomer Premises Equipment
  35. 35. Let’s Study How Telephones, One Type OfLet’s Study How Telephones, One Type Of CPE, WorksCPE, Works Example Of Some Modern Telephones
  36. 36. Direct Current (DC) - An Electrical Charge Flows Steadily In One Direction Over the Conductor. Voltage Over Time In A DC Circuit Time Voltage + - Do You Remember From TCM 134 How DC Current Flows?
  37. 37. DC Voltage Resistor R I DC Voltage Resistor R I Flows When Switch Closed DC Series Circuits With & W/O A Switch Ohm’s Law: V = I x R
  38. 38. DC Voltage Resistor R Do You Remember From TCM 134 How A Capacitor Affects Current Flow In A Circuit? Does I Flow? Does Current Flow In Circuits A Or B? Capacitor AC Voltage Resistor RCapacitor Does I Flow? Ohm’s Law: V = I x R
  39. 39. A View Of A Telephone Set
  40. 40. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # Examine The Diagram Below To See If You Can Apply Any Of The Lessons Learned From The Previous Two Slides. Under What Conditions Will Current Flow (1) Through The Ringer, (2) Through The Keypad, and (3) Into The Hybrid Coil. Closed Functional Diagram – Telephone Set
  41. 41. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # What Should The CO Switch Do First? What Should The CO Switch Do Next? Closed What Does The Central Office Do To Allow You To Dial Your Telephone?
  42. 42. A Touch Tone Phone Operates By Transmitting A Combination Of Two Frequencies Each Time A Button Is Pressed. Pressing Each Button Sends Out A Different Combination Of Frequencies. How Does DTMF Dialing Work?
  43. 43. Rotary Dialing - A User Chooses A Number And Turns A Wheel From That Number To The Finger Stop Then Releases The Wheel. Finger Stop How Does Rotary Dialing Work?
  44. 44. The Phone’s Internal Electronics Repeatedly Breaks The Electric Current To Signal The Number Dialed. The Interrupts In The Current Causes Pulses Of Specific Lengths, These Pulses Of Interrupted Current Flow Are Used In Pulse Dialing Rather Than Frequencies To Represent Each Digit. How Does Rotary Dialing Work? - Continued
  45. 45. To Dial The Number “2” The Phone’s Electronics Breaks The Current 2 Times. To Dial The Number “9” The Phone’s Electronics Breaks The Current 9 Times. Question: How Is The Number “0” Dialed? How Does Rotary Dialing Work? - Continued
  46. 46. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # How Is Current Transitioned From The Two-Wire CO Circuit To The Four Wires Required To Operate The Receiver And Transmitter? What Is An Impedance Mismatch & How Does It Apply Here? Closed Operation Of The Receiver And Transmitter
  47. 47. Carbon Filled Receiver/Transmitter Carbon Particles Used To Create Current. Transmitter - The Input Voice Alternately Compresses The Carbon Particles Which Create A Matching Oscillating Current. Receiver – The AC Current From The Telephone Wires Moves A Membrane Which In Turn Alternately Compresses The Carbon Particles Which Produces Sound.
  48. 48. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # What Is The Role Of The Hybrid Coil Or Hybrid Network? What Is The Role Of The Balancing Network? Closed Hybrid Coil And The Balancing Network
  49. 49. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # What Should The CO Switch Do First? What Should The CO Switch Do Next? Open How Does The Central Office Ring Your Telephone?
  50. 50. RingerLine From CO R T Switch Hook Hybrid Coil Balancing Network Receiver Transmitter 1 2 3 4 5 6 7 8 9 * 0 # When The Switch Hook Is Closed, Current Flows. Closed Current Current Functional Diagram – Telephone Set: Switch Hook Closed
  51. 51. The Electronics Within Each CPE Listed Earlier Works Differently. All CPE Are Similar, However, Since They All Eventually Create Electrical Signals Which Are Transmitted Over Telecommunications Wiring And Those Signals Are Received By A Compatible Piece Of CPE. Later In This Course, We Will Have The Opportunity To Study How Additional CPE Works. Summary Of CPE

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