1 / 28

Chapter 5

Chapter 5. Voice Communications. Agenda. Telephone Central office Public Switched Telephone Network Lines Signals Numbering Services Private telephone system Wireless communication. Telephone Set. Transmitter Analog signal Receiver Sidetone Switchhook On-hook and off-hook

tracy
Download Presentation

Chapter 5

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. Chapter 5 Voice Communications

  2. Agenda • Telephone • Central office • Public Switched Telephone Network • Lines • Signals • Numbering • Services • Private telephone system • Wireless communication

  3. Telephone Set • Transmitter • Analog signal • Receiver • Sidetone • Switchhook • On-hook and off-hook • Dialing • Rotary dial • Dual-tone-multifrequency (DTMF) or touch tone • Ringing • Call setup time

  4. Central Office - I • Switching equipment • Manual switching • Electromechanical switching • Step-by-step switches • Crossbar switches • Electronic switching • Reliable • One total failure in 40 years • Quite & efficient • Less Labor costs with higher skill levels • Design considerations • Forecasting demand (time, duration, distance, culture) • Grade of service or blocking

  5. Central Office - II • End office or serving central office • Toll office or switching office • Central hub

  6. Public Switched Telephone Network • Line types • Local loop (pair of copper wires: tip and ring) • Drop wire • Distribution cable • Feeder cable • Trunk • Copper wire • Coaxial cable • Microwave radio • Fiber optic cable • Internet line usage problem

  7. Analog Signals - I • Signal frequency • Sine wave • Cycle • Hertz (Hz): frequency per second • Kilohertz (kHz) • Megahertz (MHz) • Gigahertz (gHz) • Bandwidth • 0 to 4,000 Hz (between 300 and 3,000 Hz) • Guard channel or guard band (buffer)

  8. Analog Signals - II • Amplitude • Loudness • Frequency • Vibration speed • Phase • Relative position of wave measured in degree

  9. Analog Signals - III • Modulation & demodulation (voice &carrier wave • Three methods • Amplitude modulation (AM) • Frequency modulation (FM) • Phase modulation (PM) • Multiplexers • Base group, channel group or just group (12 - 4kHz) • Supergroup (5) • master group (10) • Jumbo group

  10. Time Assignment Speech Interpolation (TASI) • Pack multiple voice conversations onto a single telephone line • Eliminate 10% of quite time in conversation

  11. Inter Office Signaling • Direct current (DC) signals • Dial tone signal • Tone signals • Ringing, busy, and congestion signals • Common channel signals • Common channel interoffice signaling system (CCIS) by ITU-T • Signaling system No.7 (SS7) • Use separate lines to set up telephone calls • Optimizing the digital networks • Offer enhanced services

  12. Telephone Numbering • 9 geographic zones by ITU-T • Composition • Access code, carrier’s code, • Zone and country code • Area/city code • Exchange code • Subscriber code

  13. Telephone Services - I • Types of calls • Local calling • Long distance calls • International calls • Operator services

  14. Telephone Services - II • Calling card calls • Discounted calls • 800 service • Geographic: interstate, intrastate, international (Universal International Freephone Numbering -UIFN) • Call direction: in, out, or both • 900 service

  15. Telephone Services - III • Software defined network (SDN) • Foreign exchange (FX) lines • Integrated Services Digital Network (ISDN) • Selection criteria for telephone service • Time • Duration • Number • Location Usage pattern • Usage pattern (busy hour) • 1-5% (Blocking) grade service level

  16. Internet Telephone Calls • Voice over IP (VoIP) • Benefits • Problems • Impacts • Future

  17. Private Telephone Systems • Key systems: 3 to 50 telephones • Private branch exchange (PBX) / private automatic branch exchange (PABX) / computer branch exchange (CBX): over 50 • Tie line or tie trunk for lease line • Centrex • Communication server

  18. PBX System Features • Data communication • Direct inward dialing (DID) • Hunt group • Least cost routing • Pickup group • Station message detail recording/call detail recording (SMDR)/(CDR)

  19. PBX Station Features • Automatic reminder • Call forward • Call transfer • Call waiting • Camp on (call back) • Distinctive ringing • Do not disturb • Speed dialing

  20. PBX Security • Block remote access • Change access code and password • Block outgoing calls during off-hours

  21. Selection Criteria of PBX • Maintenance • Training • Other support • Price • System feature • Station feature • Security feature

  22. Centrex Service • Regulated by public utilities commission • PBX equipment in central office

  23. Selection CriteriaBetween PBX and Centrex • Regulation • Maintenance • Reliability • Growth • Control • Capital investment

  24. Audio Teleconferencing & Voice Mail • Audio Teleconferencing • Voice mail • Automated attendant • Audiotex • Interactive voice response

  25. Wireless Communication - I • Cordless telephone • Cellular telephone service • Transmitting voice & data • Security • Eavesdropping • Spread spectrum • Accident • Second generation systems • Time division multiple access (TDMA) • Global system for mobile communication (GSM) • Code division multiple access (CDMA)

  26. Wireless Communication - II • Cellular telephone service • Third generation systems • Japan: I-mode • European: Wireless application protocol (WAP) • Bluetooth: 33-foot radius • Marine and aeronautical telephone services • Radio communication

  27. Points to Remember • Telephone • Central office • Public Switched Telephone Network • Lines • Signals • Numbering • Services • Private telephone system • Wireless communication

  28. Discussion • Design a voice communication system for an airline

More Related