A Probe into Basic Telephony and Telecommunications

1. A Probe into Basic Telephony and Telecommunications Jon F. Johnson Extension Area Specialist Virginia Cooperative Extension

2. Telephony? • The making and operation of telephones – Webster’s New World Dictionary

3. Telecommunications • More advanced products, services, and applications of traditional telephone services that not only carry voice traffic but data as well

4. Talking Beyond the Teleset… • Cable media – copper, fiber optics, microwave • The POTS line - Plain Old Telephone Service • Analogue and Digital Telephone Signals • Circuit Switched Operations • The C.O.– The Central Office • PSTN – The Public Switched Telephone Network • Traditional and enhanced TELCO (Telephone Company) services

5. Analog Telephone Signals… • Analog transmissions began with invention of the telephone in 1876 • Analog signals move along a telephone line as an electromagnetic wave • Analog signal strength is measured by frequency and requires amplification as it travels • Analog signals can easily pick-up electrical interference or noise

6. Digital Telephone Signals… • Digital signals are transmitted as binary bits (binary means two values for bits: on and off) • Digital “on” bits carried by copper medium represent positive voltage while “off” bits represent no voltage • Bits make Bytes and the amount of transferred Bytes determines Bandwidth

7. Bandwidth • The measure of the capacity of a communications channel (path). • Digital channels are measured in bits per second. • Analog telephone lines are measured by hertz (cycle of a wave from crest to trough)

8. Digital versus Analog… • Digital signals are easily recreated as they travel along a telephone line by digital regenerators or repeaters • Unlike analog amplification, noise (static from electrical interference) is discarded • Digital service is more reliable and requires less equipment to boost signals strength

9. Switching defined… • The establishment on demand, of an individual connection from a caller to a desired receiver … as long as is required for the transfer of information. - International Telecommunications Union (ITU)

10. The Public Switched Telephone Network (PSTN) • The Central Office (CO) • The Tandem Office • The Toll Office • Interexchange Carrier’s (IEXs) Point of Presence (POP)

11. The CO defined… • A telephone company facility that houses the local switching equipment and serves as the place of termination for the wires from all telephones (the local loop) in a specified geographical area served by that telephone company. • The Exchange!

12. Who’s in the CO? • The Local Exchange Carrier or LEC • CLEC or Competitive Local Exchange Carriers - Maybe? • Interexchange Carriers or IEX (Long distance services providers) • Local ISPs - Internet Service Providers

13. The POP • Physical location for Interexchange carriers (MCI, Sprint, AT&T, etc.) or IEXs to have their Point of Presence or POP • The POP is the connection between the incumbent network and the carrier’s network.

14. An ISP is… • Internet Service Provider connects end-users to the Internet via telephone lines, cable media, or other media.

15. ISP Services • ISPs often supply services such as voice mail, web hosting, and domain name registration for websites • POTS • ISDN – Integrated Services Digital Network (protocol) via twisted pair

16. Some Telco Services • POTS • Value added services (voice mail, call waiting, conference calling, etc.) • DSL (Digital Subscriber Line) • ISDN (BRI and PRI) • ATM (Asynchronous Transmission Mode) • Frame Relay • T1, T3, DS1, DS3 • Intrastate and interstate connections • Long-distance service

17. Transmission Media • T1 uses 2 copper pairs • DS1 uses fiber optics with the same bandwidth as a 2 copper pairs • Fiber-optics cable is made from glass that transfers light and not electricity and is used for higher-speed transmissions • Coaxial cable is capable of delivering up to 10Mbps or more (voice, data, & video) • Ethernet cabling typically uses 2 of 4 pairs of Category 5 or 6 cable to deliver 10 or 100Mbps of bandwidth

18. Important Protocols for Most Consumers • DSL – Digital Subscriber Line (a glorified twisted pair with broadband capabilities 128kps to 6 Mbps with distance limitations)

19. Residential or Business? • POTS basic service - $20/mth • Dial-up internet access - $15 to $30/mth with 56kps max. capability • DSL basic service - $50/mth with 6Mbps to 128kps (download and upload) with distance limitations Note: DSL carries voice and data • Broadband cable internet service - $70/mth with 10Mbps, add $18/mth for basic voice and more for TV signal Note: broadband is a shared network

20. Government, Business, Educational Uses • T1 lines are most commonly used by larger business and government agencies with greater bandwidth needs • T1 and DS1 lines can range from $700 to $1000+/mth, depending on competition, and offer up to 1.54Mbps (64kps/channel) • T3 and DS3 offer 44.7 Mps or the equivalent of 28 T1 (that’s is a lot of money)

21. Special Notes and Recommended Resources: • Pricing is relevant to September 2002 and is based on the Richmond Metro Area • The Essential Guide to Telecom by Annabel Dodd • Verizon Communications at www.verizon.com