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Telephone Network Hierarchy Analog Sounds

Telephone Network Hierarchy Analog Sounds. ENGR 475 – Telecommunications Harding University Jon White. Voice. Voice. Voice. Voice. Sound Barrier. Telephone Network. PSTN – Public Switched Telephone Network World’s public circuit switched voice assemblage.

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Telephone Network Hierarchy Analog Sounds

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  1. Telephone Network HierarchyAnalog Sounds ENGR 475 – Telecommunications Harding University Jon White

  2. Voice

  3. Voice

  4. Voice

  5. Voice

  6. Sound Barrier

  7. Telephone Network • PSTN – Public Switched Telephone Network • World’s public circuit switched voice assemblage. • Similar to how the Internet is the assemblage of the World’s IP based packet switched networks • POTS – Plain Old Telephone Service • Analog, full duplex, dial tone, subscriber dials • 2 wires for communication (Tip and Ring) • Voice travels over a 48 V DC source provided by the Telco. • Local Loop • 2 to 25 miles of 19 AWG unshilded twisted pair • Demarc or point of presence • Line in the sand

  8. Telephone Network - Demarc

  9. Telephone Network Components • Terminals • Phones • Access • Phone lines • Connectivity • Intelligence to let phones use phone lines to call other phones • Switches • PBX – Private Branch Exchanges • Other Features • Call forwarding, re-dial, caller ID, voice mail, protocol conversion

  10. PBX – Private Branch Exchange • Almost every corporation has one. • Handles internal switching. • You don’t have to go outside your network when calling someone in your building. • Performs other helpful features • Call forwarding. • Call holding. • Caller ID • http://wandel.ca/homepage/pbx.html • With VOIP, your computer can do all this in software.

  11. Telephone Network • The Telephone Network must implement areas in Connectivity: • Provide power to the phone when picked up • Announce when ringing • The first signal we’ve talked about • Address resolution / Call routing • How is this signal passed? In band or out of band? When you press a key, what do you hear? • Provide a guaranteed QOS

  12. Telephone Hiearchy • Ring Topology • Star Topology • Hybrid

  13. Telephone Network Toll Center = Tandem Office End office = Central Office (CO) Modern CO’s serve up to 100,000 customers. Searcy’s CO

  14. Telephone Network - CO

  15. Telephone Network – Pedestal Box

  16. Telephone Network – Wiring Closet

  17. Telephone Network – Patch Panel

  18. Telephone Network Terms • Exchange Area • Local vs long distance • LEC – Local Exchange Carrier • ILEC – Incumbent LEC • CLEC • BOC – Bell Operating Company • RBOC • Trunks – fiber optical • 10 to 1 • TIE lines • LATA – Local access and transport area • IXC – Inter-exchange Carrier • Carry inter-LATA traffic

  19. Telephone Network – LATA Areas

  20. Telephone Network – After Divestiture

  21. Telephone Network - POP • POP – Point of Presence • Where are they at?

  22. Telephone Network - Connectivity • We’ve covered: • Terminals • Access • Connectivity • How a call gets routed to the proper place. • One of the most difficult parts. • Whole world has to agree. • Hard to change once you’ve started giving out ID’s • NANPA • North American Numbering Plan Association • Designed by AT &T in 1947 • In charge of managing phone numbers

  23. NANPA Map

  24. NANPA Evolution – pg. 42 • Phone numbers: • Area Code – 3 digits • Exchange Code – 3 digits • Subscriber Code – 4 digits • Area codes: • Don’t start with 1 or 0 • 1-800, 0 for operator, 1 to dial long distance • Other area codes aren’t available, 411, 211,311,911 • Around 6 billion phone numbers are currently available. • How much storage space is required to store 6 billion phone numbers using ASCII representation along with the switch they belong to? • Number portability.

  25. NANPA • Like IP addresses, we are running out of telephone numbers. • Cell phones, fax, pagers, American Idol, modems • http://telcodata.us/ - Your switch and what your phone number tells people. • http://www.nanpa.com – Available numbers in your area code, cool maps.

  26. LATA – Local Access and Transport Areas • Confusing billing! • Occurred after the 1984 At &T breakup. • Now, there are differences in how long distance your long distance call is. • Often, the LATA boundaries are arbitrary. • LATAs are smaller than area codes • If you live in Dallas, it now might cost more to call Houston than Los Angeles

  27. LATA Map

  28. LATA Terms • Intrastate, IntraLATA • Ought to be a local call • But, they can still charge “local” tariffs • Intrastate, InterLATA • Same state, different LATA • Interstate, InterLATA • Different state, different LATA • Interstate, IntraLATA • Different state, same LATA • Does this ever occur? • Telephone billing is confusing.

  29. Conclusion • In what ways is the telephone network different than the Internet? In what ways is it the same? • Some of the distinctions in billing are rapidly fading away. Why is that?

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