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Legacy Voice World

Legacy Voice World. Chapter 03. Analog Connectivity. What is analog connectivity Electric wave forms Understanding Analog signaling. Thomas Edison. Record player Braille Home telephone lines Analog phone lines electricity for voice transmission. As you speak. Analog to digital

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Legacy Voice World

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  1. Legacy Voice World Chapter 03

  2. Analog Connectivity • What is analog connectivity • Electric wave forms • Understanding Analog signaling

  3. Thomas Edison • Record player • Braille • Home telephone lines • Analog phone lines electricity for voice transmission

  4. As you speak • Analog to digital • Properties of electricity as used to convey properties of voice • Digital to analog

  5. Signaling • When receiver is on-hook, circuit is broken Loop - + Battery at the CO Tip - Ring

  6. Signaling • When receiver is off-hook, circuit is complete • This is an example of loop start Loop - + Battery at the CO Tip - Ring

  7. Signaling • This is an example of Ground start • Off-hook signal accomplished by temporarily grounding the ring wire • Stops GLARE Loop - + Battery at the CO Tip PBX - Ring

  8. Signaling over Analog Lines • On-hook • Off-hook • Ringing • Ringing is sent using AC current rather than DC

  9. When receiver is on-hook, circuit is broken • True • False

  10. Additional Signaling • Dual tone • Busy • Ring back • Congestion • Re-ordering • Receiver off-hook • No such number • Confirmation • And more

  11. Address Signaling • Pulse (70% connected and 30% broken connection) • DTMF (dual tone multi-frequency)

  12. DTMF works on • Only analog phones • Only on digital phones • Both analog and digital phones • Neither analog or digital phones

  13. What Did We Learn? • What is analog connectivity • Electric wave forms • Understanding Analog signaling

  14. Historical Voice • Problems with Analog connection • Converting Analog to Digital • Converting Digital to Analog

  15. Wiring a Problem • Distance is prohibitive for analog wiring • Requires -2 wire system CO Repeater Repeater

  16. Analog phone wiring requires • One wire • Two wire • Three wire • Four wire

  17. Sample Voice • Nyquist: If you sample at twice the highest frequency, you can accurately reconstruct a signal digitally • Common frequencies: • Human hearing 20-20,000Hz • Human speech 200-9,000Hz • Nyquist therum 300-4000Hz

  18. Quantizing the Sample PAM – Pulse Amplitude Modulation

  19. Human hearing range is 20 - 20,000Hz. Nyquist theory is what range? • 20 – 20000Hz • 200 – 20000Hz • 200 – 9000Hz • 300 – 4000Hz

  20. Convert the Sample to Binary • A-Law • U-Law (US, Canada, Japan) • 0110011 • Both use the first bit to represent “+” or “–” amplitude • A-Law uses “1” for Positive and “0” for negative • U-Law uses “0” for Positive and “1” for negative • Both use the next three bits for segments • Both use the following three bits for the interval • U-Law is known as Transcoding

  21. Consider the bit string 1011011… This represents a positive notation for ___ • A-Law • U-Law

  22. Once in Binary • Optionally compress the Samples • Send all the samples • Send just the changes • Build a code bank *standard voice sample: 64kbps (G.711) *common compressed value: 8 kbps (G.729)

  23. Which codec provides the best QoS? • G.729 • G.726 • G.723 • G.711

  24. What did we Learn? • Problems with Analog connection • Converting Analog to Digital • Converting Digital to Analog

  25. Multiple Calls on a single Pair of Wires Solve the wiring problem: TDM Understand T1, E1, and CAS specifications Understand T1, E1, and CCS specifications

  26. TDM • Carries multiple conversations over a 4 wire path • Build wire channels called DS0s • Each channel gives a time slot to transmit • Common DS0 Groups: • T1 (24 DS0 frames) • E1 (32 DS0 frames_) PBX PBX 1 1 1 1 2 2 2 2 4 4 4 4

  27. Analog Signals are Electrical Frequencies • Once voice is digitized – signals must be 1s & 0s • There are two methods: • CAS (Channel Associated Signaling) • CCS (Common Channel Signaling)

  28. CAS in a T1 Environment (RBS) Robbed Bit Signaling • The least significant bit in each 6th frame is signaling

  29. The previous chart represents ____ in a T1 environment • CCS • RBS • SS7

  30. Quality and Robbed Bits • The 6th frame missing a bit degrades quality • T1 can send Large frames of 193 bits at a time • T1 Frame bit is in the first bit in DS0 24 • T1 has two framing types: • Super framing (SF): sends 12 T1 frames at a time • Extended superframes (ESF): send 24 T1 frames at a time • F6, F12 and F18, F24 (frames referenced as “A,B,C,D”)

  31. CAS in an E1 Environment • CAS has dedicated frames and signaling in separate channels • CAS E1 has 32 channels • Ch1 – dedicated to framing • Ch17 – dedicated to signaling • Chs2 - 16 and 18 - 32 are dedicated to voice • E1 is contra-intuitive ; called CAS since each time a slot is signaled it matches to a voice channel • It is compatible with T1 CAS (has the same ABCD signaling format

  32. Bundling Channels Together on a T1 and E1 Connection • CCS (Common Channel Signaling) is simpler than CAS • CCS dedicates a signaling channel on T1 and E1 • Allows for the use of a signal protocol rather than just four bits of signaling per channel • Allows for more clmplex signaling messages • Allows for proprietary signaling messages • Most common signaling protocol is ISDN’s Q.931 • Other signaling protocols exist such as SS7 • Signaling Channel: • T 1 signaling channel 24 • E1 signaling channel 17

  33. What Did We Learn? Multiple Calls on a single Pair of Wires • Solve the wiring problem: TDM • Understand T1, E1, and CAS specifications • Understand T1, E1, and CCS specifications

  34. PSTN • Components of the PSN • Difference between PBX and Key Systems • PSTN Numbering Plans

  35. PSTN Components • Analog telephone • Local loop • Central Office (CO) • Trunks (SS7) • Trunks (CAS) • PBX • Digital Phones

  36. Trunks

  37. Which of the following is not a PSTN component • Analog telephone • PBX • CAS Trunks • Router • SS7 Trunks • Central office • Local loop

  38. Offices • PBX and Key Systems • Typical digital PSTN connection (T1 & E1) • Provide each user unique extension number • Support a large number of features • Key Systems • Typically Analog PSTN connection • Users share lines between phones • Support smaller number of features

  39. PSTN Dialing Plan • PSTN number plan managed under ITU-T E-164 standard • Country • National description code • Subscriber number North American Numbering Plan (NANP) • Country code • Area code • Central office code • Subscriber code • 1-555-510-3001 (NANP)

  40. Country code - Area code - Central office code - Subscriber codeThis numbering plan represents • E.164 • NANP • Both • None of the above

  41. What Did We Learn? • Components of the PSN • Difference between PBX and Key Systems • PSTN Numbering Plans

  42. Cisco Components of the Voice Networks • Cisco infrastructure model • Cisco Call Processing • Cisco applications options

  43. The Infrastructure Model

  44. Call Processing: UC500 • Supports 8 to 48 IP phones • Integrated Voice main and Auto-attendant • External MOH • FX0 modules for external Analog phones • FX1 modules for analog phone connections • Routing/NAT support support • VPN support • Opt 802.11 wireless

  45. Step above UC500 – CME • Supports more features than UC500 • Voice mail support added through (CUE) Cisco Unity Express • Runs on Cisco ISRs • Mostly CLI configuring

  46. Infrastructure Parts • End Points • Hardware • Applications • Infrastructure • Call processing

  47. Cisco Routers

  48. Business Edition • Provide scalability to 500 IP phones • Combines three applications into one • CCM (Cisco Communications Manager) • Cisco Unity Communications • Cisco Unified mobility • Fantastic but NO REDUNDANCY

  49. Full Blown Call Manager (CUCM) • Scales to 60,000 IP phones per cluster • Multi-server redundancy • Multi-site support • $$$

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