1、 Fundamentals of Telecommunications Overview Sometimes,when attending a class,it is okay to miss the first half-hour.After all,we do know something about the subject,and that first half-hour is likely to carry little more than introductory information.The same holds true when picking up a textbook o
2、n a particular subject.Maybe the first chapter can be skipped;again,it contains introductory material that we already know.But often this is not the case.We do not know as much as we thought we knew,and that first half-hour,or that first chapter,contains material that may well be prerequisite materi
3、al.That is what this Web ProForum tutorial is all about.It provides the equivalent of that first half-hour or that first chapter and may well be valuable in understanding the other tutorials in this series.The tutorial will cover the fundamentals of telephony,from its inception in Alexander Graham B
4、ells laboratory to todays emerging technologies.Topics 1.History and Regulation of the Telephone Industry 2.Network 3.Switching Technology 4.Transmission Media 5.Transmission Technology 6.Broadband Access and Service 7.Wireless Self-Test Correct Answers Glossary Web ProForum Tutorials http:/www.iec.
5、org Copyright The International Engineering Consortium 2/26 1.History and Regulation of the Telephone Industry Mr.Watson,come here,I want you.With these historic words Alexander Graham Bell called to his assistant Thomas Augustus Watson over the so-called telephone,and an industry was born.The place
6、:5 Exeter Place,Boston,Massachusetts The time:evening,March 10,1876 As with all inventions,the road had not been smooth.For years,Graham Bell(as he liked to be called)had been experimenting with a harmonic telegraph.It should be possible,he reasoned,to send six tones over the same wire at the same t
7、ime and cause six reeds attached to the receiving end to be operated.Furthermore,if all worked well,varied combinations of these six pitches could reproduce human speech.Simultaneously he was working on a scheme that utilized the varying resistance of a wire.A diaphragm,which would be vibrated by th
8、e human voice,was attached to a wire that was dipped into a mixture of acid and water.In theory,as the diaphragm moved downward,forcing more wire into the acid,the resistance of the wire would be decreased.As the diaphragm moved upward,the wire would be withdrawn from the conducting liquid,and its r
9、esistance would be increased.It was this device that was ultimately successful and that formed the basis for the telephone industry for many years.A year later,on July 9,1877,the Bell Telephone Company was formed,and Alexander Graham Bell became the companys electrician,at a salary of$3,000,and Wats
10、on became superintendent in charge of research and manufacturing.Unfortunately for Bell,the basic patents were due to run out in 1893 and 1894.But by this time,Theodore Newton Vail had been brought in as general manager,and he immediately set about establishing an organization strong enough to survi
11、ve without a monopoly.What we wanted to do was get possession of the field in such a way that,patent or no patent,we could control it,Vail said.The first step was to obtain a captive manufacturing facility,and this was accomplished in 1881 with the purchase of Western Electric Company.Vail also sent
12、 his salesmen into the field to set up telephone exchanges in virgin territory.Generally,local promoters were encouraged to organize a local telephone company and sell stock.Thus,by 1885 Vail had established a vertically integrated supply division,a network of companies licensed by the parent,and a
13、strong research and development arm.The expiration of Bells basic patents in 1893 and 1894 was the starting signal for open competition.Independent telephone operating companies sprang up throughout the country;by the turn of the century there were approximately 6,000 of them,and these 6,000 provide
14、d Web ProForum Tutorials http:/www.iec.org Copyright The International Engineering Consortium 3/26 service to some 600,000 subscribers.Through the years,mergers and acquisitions took their toll;at the present time there are approximately 1,300 local exchange carriers.Unfortunately for the general pu
15、blic,all of these telephones were not interconnected.Therefore,it was necessary for a subscriber to have two or three instruments to communicate with the total population of the city.However,the great asset of AT&T,which became the official name of the company at the end of 1899,was the control of a
16、ll the long-distance circuits and its steadfast refusal to interconnect any other company to it.This would never do,and the Justice Department filed suit in 1912.The world was angry with AT&T,and an AT&T vice presidentNathan C.Kingsburyrealized it.He recognized that the best demonstration of AT&T not being in a monopoly position was to point to thousands of independents apparently operating in harmony.To this end,AT&T agreed to provide interconnection arrangements to all independents.This 1913 a