1 / 69

Telephony Networking

Telephony Networking. Lesson 1: Telephony Essentials. Objectives. Define codec, and describe the G.711 protocol Define Pulse Code Modulation (PCM), and distinguish between the μ-Law and A-Law companding algorithms

eamon
Download Presentation

Telephony Networking

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. TelephonyNetworking

  2. Lesson 1:Telephony Essentials

  3. Objectives • Define codec, and describe the G.711 protocol • Define Pulse Code Modulation (PCM), and distinguish between the μ-Law and A-Law companding algorithms • Explain common feature sets for voice calls, including call waiting, call blocking, call forwarding, call monitoring, callback, and additional private network features • Explain Direct Inward Dialing (DID) • Define hunt groups • Identify elements of a call centre or contact centre, including call routing, caller ID, automatic call distributors, pop-ups, instant messaging/chat, e-mail, real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

  4. Objectives (cont’d) • Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface • Identify symptoms of improper clocking configuration (e.g., problems with synchronization) • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analogue setup messages, safety practises and standards, crosstalk, split, line imbalance, open, short, earthing issues, echo cancellation in two-wire-to-four-wire hybrids)

  5. Analogue to Digital Pulse Code Modulation (PCM) – converts analogue voice data to digital format, then back to analogue • PCM uses two compression algorithms: • Mu-Law (used only in North America and Japan) • A-Law (the standard for all international circuits) • G.711 – international standard for encoding voice on a 64-Kbps channel

  6. Exchange Connections • Point of presence (POP) – an interexchange carrier that connects long-distance services to a local connection • Private Branch Exchange (PBX) – enables an organisation to create an internal telephone-numbering system • Direct Inward Dialing (DID) / Direct Dialing Inward (DDI) – enables multiple telephone numbers to be used on a few lines

  7. Common Voice Call Features • Call waiting– suspends current call to pick up another incoming call • Call blocking– prevents calls from ringing through based on point of origination; also, restricting a station from making outbound or long-distance calls • Call forwarding– redirects calls from one phone number to a second phone number • Callback– monitors a busy phone and completes a call to that number when the busy phone goes back on-hook

  8. Additional Private Features • Call monitoring– keeps detailed records of phone transactions • Traffic reporting– reports that detail usage on incoming and outgoing trunk groups • Ringing preferences– programs certain lines to ring only on particular stations • Automated attendant– answers call, collects station number of desired party, then transfers the call • Voice mail systems– integrated voice mail • Outward restrictions– restricts stations to making only intercom or local calls • Private numbering plans– allow users to call internal extensions without using an outside line • Unified messaging– stores all forms of messaging, e-mail, voice mail and fax, in a centralized server

  9. Hunt Groups • Allow incoming calls to be routed to available alternate numbers • Most-idle line hunting– used to distribute the load over all trunks • Sequential hunting– hunts in a sequence from the dialed number through to the end of the hunt group • Circular hunting– hunts all lines in the hunt group before returning a busy signal

  10. Call / Contact Centres • Centralized office used for processing a large volume of calls • Companies use call centres to interact with their customers • Calls are automatically distributed among agents • Predictive dialers automatically dial batches of phone numbers for connection to agents • Calls are recorded for quality assurance and legal purposes • Contact centres allow for interaction with agents via phone, e-mail, chat or instant messaging, and Web (click-to-talk)

  11. Call / Contact Centre Software • Automatic call distribution (ACD)– used to distribute the load over all trunks • Interactive voice response (IVR)– allows a caller to interact with a database • Customer relationship management (CRM)– integrates with ACD software, allowing the software to query the database and display customer information on an agent’s screen • Metrics– enable supervisors to analyze performance

  12. Elements of Computer-Telephony Integration (CTI) • Calling line information display • Authentication of callers • Interactive voice response to callers • Live voice or touchtone input • On-screen pop-ups • On-screen dialing and phone control • Receiving and routing fax messages • Logging on • Agent instruction • State control • Multi-channel blending • Managing voice or video conferences • Call routing and reporting

  13. Hosted Solution Benefits • Relatively short and simple start-up cycles • Eliminates the need for specialized staff • Tech support and maintenance handled by hosting company • Allows for maximum flexibility in agent placement and routing of incoming calls to agents • Enables a “virtual call centre”

  14. Trunks and Signaling • Analogue loop-start trunks used in most standard home phones • Earth-start trunk lines often used to connect a PBX to an exchange

  15. The Primary Reference Source • Primary reference source (PRS) – a hierarchical system wherein a super-accurate time source is defined as stratum-0; used to time and synchronize digital connections • PRS strata • Stratum 1 – extremely accurate; usually provided by a GPS-enabled device • Stratum 2 – at one time used by long-distance providers, but now largely out of use • Stratum 3/3E – used by public exchanges, gatekeepers and gateways • Stratum 4 – used by PBXs and telco channel banks

  16. PRS (cont’d) • Timing types • Asynchronous – no timing information is shared • Synchronous – a common system clock is used for all trunk lines and networks involved • Plesiosynchronous – a number of PRS clocks are used for all networks involved • Symptoms of improper clocking • Audible pops and clicks • Loss of data

  17. Cabling and Wiring • Service wire centre – houses one or more local switching systems • Main distribution frame (MDF) – the main interface between the telco's lines and all internal lines • Patch panel – interconnects voice and data lines with RJ-11 and/or RJ-45 connectors

  18. Call-Processing Steps • Placing a call • Call setup – the connection is built between the local loop and the exchange • Call connection maintenance – the connection is established and maintained • Call completion – breaking the connection • Common analogue transmission impairments • Loss – parts of the transmission are dropped • Echo – parts of the conversation are repeated • Noise – unwanted energy that interferes with the signal • Crosstalk – parts of another conversation are heard • Echo cancellation in hybrid networks • When two-wire and four-wire networks are connected, a hybrid network is created, which can result in echo • An echo canceller balances the ohm levels between the lines, thereby eliminating the echo

  19. Summary • Define codec, and describe the G.711 protocol • Define Pulse Code Modulation (PCM), and distinguish between the μ-Law and A-Law companding algorithms • Explain common feature sets for voice calls, including call waiting, call blocking, call forwarding, call monitoring, callback, and additional private network features • Explain Direct Inward Dialing (DID) • Define hunt groups • Identify elements of a call centre or contact centre, including call routing, caller ID, automatic call distributors, pop-ups, instant messaging/chat, e-mail, real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

  20. Summary (cont’d) • Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface • Identify symptoms of improper clocking configuration (e.g., problems with synchronization) • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analogue setup messages, safety practises and standards, crosstalk, split, line imbalance, open, short, earthing issues, echo cancellation in two-wire-to-four-wire hybrids)

  21. Lesson 2:Boundaries, Numbers, Wiring and Safety

  22. Objectives • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analogue and/or digital butt set, volt metre, time domain reflectometre) • Identify safety procedures for working with convergent network equipment (e.g., power, proper earthing, electrostatic discharge [ESD], radio frequency interference [RFI], electromagnetic interference [EMI])

  23. Network Termination and Test Point (NTTP) • Network termination and test point (NTTP) • The point at which the telco’s network ends and connects with the wiring of the customer premises • Operational control or ownership of services changes here • Minimum point of entry (MPOE) – the point where telco equipment ends and inside local-loop wiring begins

  24. Telephone Numbers • Global numbering plans • ITU Recommendation E.164 establishes standards for numbering plans • Telephone numbers should not exceed 15 characters • National numbering plans • Define the numbering structure for a specific country or group of countries • Regional numbering plans • Define the numbering structure for a specific geographic region • Private numbering plans • Allow companies to create their own numbering systems

  25. Signaling Types • Three types of signaling: • Rotary / pulse or multifrequency (MF) – used on rotary dial phones • Dual-Tone Multifrequency (DTMF) – generated by touch-tone pads on all standard phones • Digital – does not process audible tones

  26. RJ-11 Connectors and Wiring

  27. RJ-12 Modular Connector

  28. BT-431A Connectors

  29. BT-631A Connectors

  30. Line Jack Units • Three types of line jack units: • Master • PBX master • Secondary • Master line jack units contain: • A 26-amp surge protector • A 1.8 uf, 250-volt capacitor • A 470-ohm service resistor • Six terminals designed to accept wiring from the wall

  31. Wall Jack Wiring Diagram

  32. Common Telephony Issues • Quality assurance and business continuity • Uptime – the length of time a device has remained operational • Mean time between failure (MTBF) – the predicted amount of time a device will function before it requires maintenance or replacement • Mean time to repair (MTTR) – the time it will take to discover the failure and repair or restore service • Availability – the length of time a device or system is able to provide service • Availability = MTBF / MTBF + MTTR • Return on investment (ROI) – the calculations made to ensure that equipment will result in company profitability

  33. Common Telephony Issues (cont’d) Telecommunications reliability issues: • Extreme temperatures • Lightning • Power requirements and heat • Electrical safety • Vibration and shock • Earthquake • Humidity • Contaminants • Fire • EMI immunity • Noise • Altitude

  34. Common Telephony Issues (cont’d) • Electromagnetic compatibility • Electrostatic discharge (ESD) – An uncontrolled buildup of electrical current • Radio frequency interference (RFI) – A signal that causes another device to operate improperly • Electromagnetic interference (EMI) – interference produced by electromechanical devices • Solutions for electrical issues: • EMI suppression filters • Capacitors • Inductors • Shielding • Ensuring proper humidity

  35. Common Telephony Issues (cont’d) • Personnel safety concerns and procedures • Tools • Loose clothing • Metal • Safety glasses • EMI, ESD and tools • Never work alone • Dust • Other problems

  36. Testing Laboratories • Testing laboratory rooms and equipment • Fire, heat, humidity and moisture • Airborne contaminant • Electromagnetic • Shakers • Wind and rain • Pressure • Sound

  37. Securing Equipment • Physically secure telephony equipment using brackets • Isolate power sources by earthing them properly • Earthing ring • Earthing lugs • Steel rod placed roughly 2 metres in the earth

  38. Summary • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analogue and/or digital butt set, volt metre, time domain reflectometre) • Identify safety procedures for working with convergent network equipment (e.g., power, proper earthing, electrostatic discharge [ESD], radio frequency interference [RFI], electromagnetic interference [EMI])

  39. Lesson 3:Troubleshooting

  40. Objectives • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analogue setup messages, safety practises and standards, crosstalk, split, line imbalance, open, short, earthing issues, echo cancellation in two-wire-to-four-wire hybrids) • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analogue and/or digital butt set, volt metre, time domain reflectometre) • Identify symptoms of improper clocking configuration (e.g., problems with synchronization)

  41. Short (continuity) Open (open fault) Terminator Cross Polarity Split Line imbalance Crosstalk Loopback testing End-to-end testing Troubleshooting Terms

  42. Troubleshooting Tools • Telephone line-test set • Also called a butt set or handset • Used to test line quality • Used to check line polarity • Used to determine loss of current • End-to-end and loopback testing • A butt set is used to generate tones and frequencies to test lines • Can use analogue butt set to listen to digital communications by going into "data safe mode"

  43. Troubleshooting Tools (cont'd) • Tone-and-probe kit • A tone generator emits tones across a wire • A probe listens on the other end of the wire for tones emitted by the tone generator • Uses • Identify open circuits • Locate short circuits • Identify breaks in a cable • Test polarity of a line • Determine line voltage • Identify lines that are causing crosstalk • Find a single conducting wire in a bundle of wires • Provide talk battery power to test a line with no dial tone

  44. Troubleshooting Tools (cont'd) • Multimetre • Measures resistance, current and voltage in an electrical circuit

  45. Troubleshooting Tools (cont'd) • Punchdown tool • Inserts wires in 66 and 110 punchdown blocks • Line tester • Determines whether a short exists in a line • DTMF decoder • Can capture, convert and play back DTMF signals • Modular breakout adapter • Breaks out all wires in a BT-431A, RJ-11 or RJ-45 jack into individual, easily accessible wires

  46. Troubleshooting Analogue Lines • PBX and earth-start analogue lines • At the PBX, use a butt set to isolate crosstalk to determine whether the problem is within or outside the building • Securing connections with a punchdown tool • Poorly closed connections or improperly set lines can cause line noise • Checking for line noise • Use a digital multimetre to measure for AC voltage • AC voltage > 1 volt = improper earthing

  47. Troubleshooting Digital Lines • Improper clocking configuration • Voice and data lines must be precisely synchronized using the exchange’s PRS • Use a butt set to check for improper clocking • Crossed signaling methods • Lines that use in-band signaling should not be directly connected to lines that use out-of-band signaling • Failed transmissions or garbled data can result • Check for proper termination • Be aware of different ISDN voice-encoding standards

  48. Troubleshooting Digital Lines (cont'd) • Consider signal-to-noise ratio • Test equipment for digital networks • Signal/spectrum analyzer • Multimetre • Oscilloscope • Time domain reflectometre (TDR) • Service-specific test set

  49. Troubleshooting Digital Lines (cont'd) • Telephones and ring voltage • REN value determines the ringing voltage • -90 v AC charge needed to ring a standard analogue telephone • Telco will not guarantee a phone to ring if a line has to service a number of devices that together constitute more than 4 REN in the UK (5 REN in North America) • Safety • Ensure that power is connected properly at the electrical termination device. • Use a residual current device (RCD) to guard against electrical shocks

  50. Summary • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analogue setup messages, safety practises and standards, crosstalk, split, line imbalance, open, short, earthing issues, echo cancellation in two-wire-to-four-wire hybrids) • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analogue and/or digital butt set, volt metre, time domain reflectometre) • Identify symptoms of improper clocking configuration (e.g., problems with synchronization)

More Related