1. Telephony Networking

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

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)

51. Lesson 4: Analogue and Digital Signaling

52. Objectives
Identify basic ISDN services and protocols, including time slots, channels, ISDN2e/Basic Rate Interface (BRI), ISDN30/Primary Rate Interface (PRI)
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)
Define the Q.931, Q.932, I.430 and Q.921/High-level Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.)

53. Objectives (cont’d)
Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface
Define QSIG, H.450 (including supplementary services), Digital Access Signaling System 1 (DASS1), private networking, and Digital Private Network Signaling System (DPNSS)
Define Signaling System 7 (SS7)/Common Channel Signaling 7 (C7) functions, including call setup, management and teardown; signaling links; signaling points (e.g., service switching point [SSP], signal transfer point [STP], service control point [SCP])

54. Signaling Categories Signaling categories:
Supervision – detects changes to a particular line
Addressing – responsible for routing signals to the correct switch
Alerting – audible alert signals
Call progress – signals that maintain calls

55. In-Band and Out-of-Band Signaling
In-band signaling
The process of allowing the control signal to share the same path as the voice and data
Out-of-band signaling
The process of using a separate channel for signaling purposes

56. Loop-Start Analogue Trunk Signaling

57. Integrated Services Digital Network (ISDN)
ISDN can carry voice, fax, imaging or data communications
Two types of ISDN:
Basic Rate Interface (BRI) – Two 64-Kbps channels for voice or data; one 16-Kbps channel for signaling
Primary Rate Interface (PRI) – Kbps channels for voice or data; two 16-Kbps channels for signaling
B channel (bearer channel) – carries voice or data
D channel (delta channel) – carries signaling

58. ISDN Protocols
I.430 – explains how the ISDN interface uses the physical and data link layers of the OSI/RM (Layers 1 and 2, respectively)
ISDN interfaces must use reference points between the telco and the end station:
U interface
S interface
T interface
Network termination equipment (NTE)
Terminal adapter
Terminal equipment

59. ISDN Protocols (cont'd)
High-level Data Link Control – Link Access Protocol D channel (HDLC–LAPD)
Used in ISDN connections to provide signaling
LAPD also known as Q.921
LAPD operates solely in the D channel of an ISDN line
LAPD provides flow control and data reliability
Q.931 and Q.932
Q.931 manages how a session is begun and ended
Q.932 makes it possible to modify connections that are already under way

60. Private Integrated Services Network (PISN)
A private network providing services to a specific set of users (not to the general public)
Formed when digital PBXs communicate with one another over private ISDN lines
Communications can be private and encrypted
A private numbering plan can be implemented
A PINX is a piece of equipment (such as a PBX and/or other networking equipment, such as a router) used to create a PISN
PINX provides automatic connection-handling functions

61. PISN Signaling Methods
Digital Private Network Signaling Scheme (DPNSS) – a collection of protocols that enable PBX-to-PBX communication over ISDN lines
Tromboning – a problem that occurs when a second connection is opened unnecessarily to accommodate a call that is being re-transferred back from one PINX to another
QSIG – the de facto standard for PISNs connected by PINX equipment through ISDN lines
QSIG basic services – enable PISN elements to establish voice and data calls
QSIG supplementary services – help control remote PINXs built by different manufacturers
Additional network features (ANF) – signaling enhancements that help handle calls

62. PISN Signaling Methods (cont'd)
QSIG basic call (QSIG BC)

63. Q and C Reference Points
Q reference point – the point at which a logical PINX interface communicates with a remote PINX
C reference point – the physical interface between a PINX and a trunk line

64. Signaling System Seven (SS7)
Signaling System Seven (SS7) – a packet-switched network protocol used by telcos in calls that pass between switches
SS7 network and protocols are used for:
Basic call setup, management and teardown
Wireless services such as internetwork roaming
Toll-free and toll services
Local number portability
Enhanced calling features
High-level Data Link Control (HDLC) – a protocol that divides signaling data into discrete packets
HDLC frame

65. Signaling System Seven (SS7) (cont'd)
SS7 elements:
Service Switching Point (SSP)
Signaling Transfer Point (STP)
Service Control Point (SCP)
SS7 signaling links:
Access (A) links – connect SSPs to STPs
Bridge (B) links – connect STP pairs in the same level of the SS7 hierarchy
Cross (C) links – connect each STP in a mated pair to its mate
Diagonal (D) links – connect STP pairs on different levels of the SS7 hierarchy
Extended (E) links – connect an SSP to an alternative STP pair
Fully associated (F) links – connect mobile network SSPs directly to each other

66. Computer-Telephony Integration (CTI)
CTI – the ability for telephony networks and data networks to share data

67. Summary
Identify basic ISDN services and protocols, including time slots, channels, ISDN2e/Basic Rate Interface (BRI), ISDN30/Primary Rate Interface (PRI)
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)
Define the Q.931, Q.932, I.430 and Q.921/High-level Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.)

68. Summary (cont’d)
Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface
Define QSIG, H.450 (including supplementary services), Digital Access Signaling System 1 (DASS1), private networking, and Digital Private Network Signaling System (DPNSS)
Define Signaling System 7 (SS7)/Common Channel Signaling 7 (C7) functions, including call setup, management and teardown; signaling links; signaling points (e.g., service switching point [SSP], signal transfer point [STP], service control point [SCP])

69. Telephony Networking Telephony Essentials
Boundaries, Numbers, Wiring and Safety
Troubleshooting
Analogue and Digital Signaling