, because the two are inextricably intertwined. In 1876, Alexander Graham Bell, a part-time inventor and Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Access Technologies a teacher of hearing-impaired students, invented the telephone while attempting to resolve the challenge of transmitting multiple telegraph signals over a shared pair of wires. His invention changed the world forever. In 1896, a mere 20 years later, Italian engineer and inventor Guglielmo Marconi developed the spark gap radio transmitter, which eventually allowed him to transmit long-wave radio signals across the Atlantic Ocean as early as 1901. Like Bell, his invention changed the world; for his contributions, he was awarded the Nobel Prize in 1909. It wasn't until the 1920s, though, when these two technologies began to dovetail, that their true promise was realized. Telephony provided interpersonal, two-way, high-quality voice communications, but required the user to be stationary. Radio, on the other hand, provided mobile com- munications, but was limited by distance, environmentally induced sig- nal degradation, and spectrum availability. Whereas telephony was advertised as a universally available service, radio was more of a catch- as-catch-can offering that was subject to severe blocking. If a system could be developed that combined the signal quality and ubiquity of tele- phony with the mobility of radio, however, a truly promising new service offering could be made available. Today, cellular telephony (and other services like it) provides high- quality, almost ubiquitous, wireless telephone service. Thanks to advances in digital technology, wireless telephony also offers services identical to those provided by the wired network. And pricing for wired and wireless services are now reaching parity: Flat-rate nationwide pricing models are commonpl