TELECOMMUNICATIONS CONCEPTS

1. TELECOMMUNICATIONS CONCEPTS & COMPONENTS Trunks, Lines & Loops Thought For The Week No Question Is A Bad Question!

2. Key Point A Loop Is Like a Road That Can Carry Different Types of Traffic. The Type, Or Size, Of A Road Can Influence The Type Of Volume of Traffic The Road Can Carry.

3. LESSON OBJECTIVES In This Lesson, We Will Review the “Products” of the Telecommunications Business: the Main Methods of Transmitting Information Across a Connection. • At The End Of Lesson 3, You Should Be • Able To: • Explain the Difference Between A Trunk And • A Line • Describe The Most Common Types Of Local • Loops • Explain The Difference Between Analog And • Digital Signals

4. Telecommunications Terms The Telecommunications Industry Uses Several Special Terms To Define And Classify Its Transmission Services. Central Office - A Telephone Facility Where Telephone User’s Lines And Trunks (Local Loops) Are Joined To Switching Equipment (Class 5 Switch) That Connects Telephone Users To Each Other.

5. Telecommunications Network Distant Central Office (212) 123-…. Residential Line Circuits FX Trunk Local Central Office Local Central Office (732) 560-…. (732) 435-…. Tie Trunk OUT-WATS CO Trunks In-WATS OUT-WATS CO Trunks In-WATS DID Trunks PBX PBX Station Line Circuits Station Line Circuits

6. Lines • A Line Is A Circuit That Connects An Individual Telephone To A Telephone Switch Such As A Class 5 Central Office Switch Or A PBX. • A Line Can Be More Generally Understood As A Transmission Path That Connects: • A Piece Of CPE To A Class 5 Switch At A Central Office. • An Employee’s User Equipment Such As A Telephone, Fax Machine, Etc. To A PBX.

7. Residential Line Circuit • Residential Line Circuits Are Usually Made Up Of One • Pair Of Copper-Wire Cable For Each Circuit. Class 5 CO Switch • A Residential Customer’s Line Circuit May Be Joined • In The Local Loop With Other Lines To Form A • Multi-Pair Cable Such As A 100-Pair Cable. • What Are The End-Points Of A Residential Circuit?

8. Business Line Circuits • For Businesses With A PBX, Line Circuits Are Pairs Of • Copper-Wire Cable For Each Circuit. Internal Business Lines Business Trunks Class 5 CO Switch • The Cabling From The PBX To The Central Office • Class 5 Switch Is Classified As A Trunk. • What Are The End-Points Of A Business Trunk?

9. Business Line Circuits - Continued • It Is Recommended That Line Circuits Within • Commercial Buildings Be Installed To Meet Standards • Specified Within The EIA/TIA 568 And EIA/TIA 569 • Standards. • EIA/TIA 568 – Commercial Building • Telecommunications Cabling Standard • EIA/TIA 569 - Commercial Building Standard For • Telecommunications Pathways And Spaces

10. Local Loop A Loop, Or Local Loop, Is The Physical Connection That Links the Demarc At The Customer Premises To The Telephone Company CO. Class 5 CO Demarc Local Loop

11. Loops • The Local Loop Can Be Formed By Several Suitable Transmission Media, Including: • Copper Wire • (Ex. 4-Pair UTP) • Optical Fiber • (Ex. 2-Pair)

12. Loops - Continued • The Local Loop Can Be Formed By Any Suitable Transmission Medium, Including: • Coax Cable • (Ex. Plenum) • Wireless Link Wireless NIC

13. Trunks • A Trunk Specifically Describes The Connection Between Switching Systems. • Trunks Can Be Classified According To Three Major Characteristics: • Direction • Capacity • Transmission Type

14. Trunk Directions • Trunks Are Offered To Business Customers In Three Configurations: • Incoming Trunks Carry Calls From A CO • Switch To A PBX. • Outgoing Trunks Carry Calls From A PBX To • A CO. • Two-Way Trunks Can Be Used For Both • Making and Receiving Calls.

15. Trunk Directions - Continued • Can You Identify A Type Of Business That • Might Use Incoming Trunks? • Can You Identify A Type Of Business That • Might Use Outgoing Trunks? • What Is A Business Incentive For A Business • To Install Incoming Trunks and/Or Outgoing • Trunks?

16. Trunk Capacity Capacity Means The Information-Carrying Ability Of A Telecommunications Facility. Trunks Usually Have Higher Capacities Than Single Lines. The Capacity Of A Trunk Can Be Measured By The Number Of Individual Lines It Provides. Trunk Capacity Is Also Expressed As The Number of Channels the Trunk Can Carry.

17. Analog Transmission • “Analog” Means a Signal Is Carried As A Pattern Of Continually Changing Waves. • There Are Two Basic Qualities Of An Analog Signal: • Frequency • Amplitude

18. Analog Transmission Frequency Refers To The Number Of Times Per Second a Wave Swings Back and Forth In A Cycle From Its Beginning Point To Its Ending Point. On The Frequency Diagram, The High-Frequency (Closely Spaced) Waves Would Create A High- Pitched Sound, And The Low-frequency (Loosely Spaced) Waves Would Create A Low-Pitched Sound. Frequency Varies

19. Analog Transmission Amplitude Refers To The Height Of A Wave, Or How Far From The Center The Wave Swings. On The Amplitude Diagram, The Frequency Does Not Change, But The Amplitude Does. Amplitude Varies

20. Channels and Bandwidths The More Frequencies A Medium Can Handle, The More Channels Of Information It Can Carry. Each Assigned Slice of Frequencies Is Called a Band. The Information-Carrying Capacity Of An Analog Transmission Path Is Called Its Bandwidth.

21. Channels and Bandwidths A Channel Is a Basic Building Block Of Business Telephone Service. This Process Of Dividing Or Combining Individual Channels Is Accomplished By Using A Device Called A Multiplexer (Mux).

22. Digital Transmission Digital Communication Is A Newer Technology That Forms The Basis For Today’s Telecommunications Networks, Services, And Systems. Digital Technology Is Now Being Used To Carry Many Types Of Signals On The Same Physical Media, And Often At The Same Time.

23. Digital Transmission “On” Bits Represents A 1 And “Off” Bits Represents A 0. When Bits Are Transmitted Over Wires, A “0” Is Represented By The Absence Of Electricity, And A “1” Is Represented By The Presence Of Electricity.

24. Digital Transmission • Two Reasons Why Digital Technologies Create More Accurate and Clearer Voice Communication Are: • First, Digital Bits Can Only Be on or off. • Second, Digital Transmission Makes It Easier to • Distinguish Between Signal and Distortion, or “Noise.”

25. Digital Transmission Digital Signals Are Susceptible To Distortion They Are More Reliable Because Electronic Equipment Can More Easily Recognize The Original Pattern Of High And Low Electrical Current.

26. Pulse Code Modulation (PCM) The Analog Vibrations That Represent The Sound Of Your Voice Are Converted Into Digital Electrical Impulses Through A Technique Called Pulse Code Modulation (PCM). PCM Is A Sampling Technique. Each Of The Samples Is Converted Into An 8-Bit Code That Represents The Frequency And Amplitude Of That Sample Of Sound.

27. Multiplexing Multiplexing Is A Method That Allows Multiple Digital Messages To Share The Same Communications Channel. To Understand Multiplexing, Imagine Three Groups Of People Lined Up To Board The Same Escalator.

28. Multiplexing • The MUX (An Electronic Device In Real Life) Allows One Person From Each Group To Board In Turn. • The Pattern Will Repeat With Another Person From Each Group, Until All Have Boarded. • There Are Two Dominant Types of Multiplexing: • Time Division Multiplexing (TDM) • Frequency Division Multiplexing (FDM)

29. Time-Division Multiplexing (TDM) The Process Of Encoding Two Or More Digital Signals Or Channels Onto One Media (Wire, Air, Fiber, Etc.). The Reason That We Multiplex Channels Together In Communications Is Because It Saves Money. One Example Of Time Division Multiplexing Is A T1. A T1 Contains 24 Channels.

30. Time-Division Multiplexing (TDM) Imagine The Difference In Cost Of Transporting 24 User Channels From New York To Los Angeles Using 24 Individual Pairs Of Wires (48 Wires) Vs. Using 4 Wires If A T1 Is Used As The Transport.

31. Digital Bandwidth The Information-Carrying Capacity Of A Digital Line or Trunk Is Expressed As The Number Of Bits It Can Transmit Per Second. Digital Bandwidth Is Commonly Measured In Kbps And Megabits Per Second (Mbps).

32. Special Access Trunks • Trunks Can Come In A Variety Of Capacities, And Provide Various Types Of Service. • Some Of The More Common Special Uses For Trunks Are: • Tie Lines • Private Lines • Foreign Exchange (FX) • Ring Down • Trunk Pricing

33. Tie Lines A Tie Line Is A Dedicated Circuit, Connected Through A CO That Links Two Points Without Having To Dial A Telephone Number. A Tie Line May Be Accessed By Lifting A Telephone Handset, or Pushing A Few Buttons. Many Tie Lines Provide Seamless Background Connections Between Different Business Systems.

34. Private Lines A Private Line Creates An End-To-End, On-All- The-Time Connection Between Two Locations. Each Private Line Is Connected Through A CO. Private Lines Are More Popular For Data Applications Than Voice. Private Lines Are Typically Billed A Flat Rate Per Month Based On The Amount Of Bandwidth Leased And Number Of Airline Miles Between The Two Connection Points.

35. Foreign Exchange (FX) Foreign Exchange (FX) Refers To A Foreign Exchange Trunk. In This Case, “Foreign” Means A Non-local CO. Companies Use FX Trunks To Provide Local Numbers in Cities Where the Companies Do Not Have Offices. FX Trunks Are Also Used To Transfer Data Between Two Distant Locations, Because They Provide High Bandwidth And Security.

36. Foreign Exchange (FX) An FX Trunk Starts at the Customer’s Location, As Shown on the FX Diagram, Connects To The Local CO DACS, and Extends From There To A Foreign CO Anywhere in the Country.

37. Ring Down A Ring Down Circuit Is A Special Telephone Line That Rings A Particular Destination Telephone As Soon As The Caller Picks Up The Handset. Type of Dedicated Line That Permanently Connects Two Telephones; A Ring Down Line Cannot Be Used To Call Other Numbers. Ring Down Trunks Are Used To Connect One Station Directly To Another.

38. Trunk Pricing Trunks Are Acquired Based On How Much They Are Used. Companies Get Flat-Rate Trunks; The Company Pays A Fixed Monthly Fee And Can Use The Trunk As Much As Necessary. Companies That Only Need To Use a Trunk Part- Time, Trunks Are Available On a Measured-Use Basis.