A preview of communications would be incomplete without a history of the subject. In this final section of this introductory chapter we present some historical notes on communications; each paragraph focuses on some important and related events. It is hoped that this material will provide a sense of inspiration and motivation for the reader.

In 1837, the telegraph was perfected by Samuel Morse, a painter. With the words'What hath God wrought,' transmitted by Morses electric telegraph between Washington, D.C，and Baltimore, Maryland, in 1844, a completely revolutionary means of realtime, long-distance communications was triggered. The telegraph is the forerunner of digital communications in that the Morse code is a varitsble-length ternary code using an alphabet of four symbols: a dot, a dash, a letter space, and a word space; short sequences represent frequent letters, whereas long sequences represent infrequent letters. This type of signaling is ideal for manual keying. Subsequently, Emile Baudot developed a fixed-length binary code for telegraphy in 1875. In Baudots telegraphic code, well-suited for use with teletypewriters, each code word consists of five equal-length code elements, and each element is assigned one of two possible states: a mark or a space (i.e., symbol 1 or 0 in todays technology).

In 1864, James Clerk Maxwell formulated the electromagnetic theory of light andpredicted the existence of radio waves; the underlying set of equations bears his name. The existence of radio waves was established experimentally by Heinrich Hertz in 1887. In 1894, Olives Lodge demonstrated wireless communication over a relatively short distance(150 yards}. Then, on December 12, 1901, Guglielmo Marconi received a radio signal at Signal Hill in Newfoundland; the radio signal had originated in Cornwall, England, 1700 miles away across the Atlantic. The way was thereby opened toward a tremendous broad-erring of the scope of commumcations. In 1906, Reginald Fessenden, a self-educated academic, made history by conducting the first radio broadcast.

In 1875, the telephone was invented by Alexander Graham Bell, a teacher of the

deaf. The telephone made real-time transmission of speech by electrical encoding and

People to talk over short distances only.When telephone service was only a few years old, interest developed in automating it. Notably, in 1897, A. B. Strowger, an under -taker from Kansas City, Missouri, devised the automatic step-by-step switch that be -ars his name; of all the electromechanical switches devised over the years, the 5trowger switch was the most oovular and widely used.

In 1904, John Ambrose Fleming invented the vacuum-tube diode, which paved the way for the invention of the vacuum-tube triode by Lee de Forest in 1906. The discovery of the triode was instrumental in the development of transcontinental telephony in 1913 and signaled the dawn of wireless voice communications. Indeed, until the invention and Perfection of the transistor, the triode was the supreme device for the design of electronic Amplifiers.

In 1918, Edwin H. Armstrong invented thel superheterodyne radio receiver; to this day, almost all radio receivers are of this type. In 1933, Armstrong demonstrated another revolutionary concept, namely, a modulation scheme that he called frequency modulation(FM); Armstrongs paper making the case for FM radio was published in 1936.

The first all-electronic television system was demonstrated by Philo T. Farnsworth in 1928, and then by Vladimir K. Zworykin in 1929. By 1939, the British Broadcasting Corporation (BBC)was broadcasting television on a commercial basis.

In 1928, Harry Nyquist published a classic paper on the theory of signal transmission in telegraphy. In particular, Nyquist developed criteria for the correct reception of tele-graph signals transmitted over dispersive channels in the absence of noise. Much of Ny-quists early work was applied later to the transmission of digital data over dispersive channels.

In 1937, Alec Reeves invented pulse-code modulation (PCM) for the digital encoding of speech signals. The technique was developed during World War II to enable the en-cryption of speech signals; indeed, a full-scale, 24-channel system was used in the field by the United States military at the end of the war. However, PCM had to await the discovery of the transistor and the subsequent development of large-scale integration of circuits for its commercial exploitation.

In 1943, D. O. North devised the matched falter for the optimum delection of a known signal in additive white noise. A similar result was obtained in 1946 independently by J. H. Van Vleck and D. Middleton, who coined the term matched falter.

In 1947, the geometric representation of signals was developed by V. A. Kotelnikovin a doctoral dissertation presented before the Academic Council of the Molotov Energy Insititute in Moscow. This method was subsequently brought to full fruition by John M.Wozencraft and Irwin M. Jacobs in a landmark textbook published in 1965.

In 1948, the theoretical foundations of digital communications were laid by Claude Shannon in a paper entitled 'A Mathematical Theory of Communication.' Shannons paper was received with immediate and enthusiastic acclaim. It was perhaps this response that emboldened Shannon to amend the title of his paper to 'The Mathematical Theory of Communication' when it was reprinted a year later in a book co-authored with Warren Weaver. It is noteworthy that prior to the publication of Shannons 1948 classic paper, it was believed that increasing the rate of information transmission over a channel would increase the probability of error; the communication theory community was taken by surprise when Shannon proved that this was not true, provided that the transmission rate was below the channel capacity. Shannons 1948 paper w

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A preview of communications would be incomplete without a history of the subject. In this final section of this introductory chapter we present some historical notes on communications; each paragraph focuses on some important and related events. It is hoped that this material will provide a sense of inspiration and motivation for the reader.

In 1837, the telegraph was perfected by Samuel Morse, a painter. With the words'What hath God wrought,' transmitted by Morses electric telegraph between Washington, D.C，and Baltimore, Maryland, in 1844, a completely revolutionary means of realtime, long-distance communications was triggered. The telegraph is the forerunner of digital communications in that the Morse code is a varitsble-length ternary code using an alphabet of four symbols: a dot, a dash, a letter space, and a word space; short sequences represent frequent letters, whereas long sequences represent infrequent letters. This type of signaling is ideal for manual keying. Subsequently, Emile Baudot developed a fixed-length binary code for telegraphy in 1875. In Baudots telegraphic code, well-suited for use with teletypewriters, each code word consists of five equal-length code elements, and each element is assigned one of two possible states: a mark or a space (i.e., symbol 1 or 0 in todays technology).

In 1864, James Clerk Maxwell formulated the electromagnetic theory of light andpredicted the existence of radio waves; the underlying set of equations bears his name. The existence of radio waves was established experimentally by Heinrich Hertz in 1887. In 1894, Olives Lodge demonstrated wireless communication over a relatively short distance(150 yards}. Then, on December 12, 1901, Guglielmo Marconi received a radio signal at Signal Hill in Newfoundland; the radio signal had originated in Cornwall, England, 1700 miles away across the Atlantic. The way was thereby opened toward a tremendous broad-erring of the scope of commumcations. In 1906, Reginald Fessenden, a self-educated academic, made history by conducting the first radio broadcast.

In 1875, the telephone was invented by Alexander Graham Bell, a teacher of the

deaf. The telephone made real-time transmission of speech by electrical encoding and

People to talk over short distances only.When telephone service was only a few years old, interest developed in automating it. Notably, in 1897, A. B. Strowger, an under -taker from Kansas City, Missouri, devised the automatic step-by-step switch that be -ars his name; of all the electromechanical switches devised over the years, the 5trowger switch was the most oovular and widely used.

In 1904, John Ambrose Fleming invented the vacuum-tube diode, which paved the way for the invention of the vacuum-tube triode by Lee de Forest in 1906. The discovery of the triode was instrumental in the development of transcontinental telephony in 1913 and signaled the dawn of wireless voice communications. Indeed, until the invention and Perfection of the transistor, the triode was the supreme device for the design of electronic Amplifiers.

In 1918, Edwin H. Armstrong invented thel superheterodyne radio receiver; to this day, almost all radio receivers are of this type. In 1933, Armstrong demonstrated another revolutionary concept, namely, a modulation scheme that he called frequency modulation(FM); Armstrongs paper making the case for FM radio was published in 1936.

The first all-electronic television system was demonstrated by Philo T. Farnsworth in 1928, and then by Vladimir K. Zworykin in 1929. By 1939, the British Broadcasting Corporation (BBC)was broadcasting television on a commercial basis.

In 1928, Harry Nyquist published a classic paper on the theory of signal transmission in telegraphy. In particular, Nyquist developed criteria for the correct reception of tele-graph signals transmitted over dispersive channels in the absence of noise. Much of Ny-quists early work was applied later to the transmission of digital data over dispersive channels.

In 1937, Alec Reeves invented pulse-code modulation (PCM) for the digital encoding of speech signals. The technique was developed during World War II to enable the en-cryption of speech signals; indeed, a full-scale, 24-channel system was used in the field by the United States military at the end of the war. However, PCM had to await the discovery of the transistor and the subsequent development of large-scale integration of circuits for its commercial exploitation.

In 1943, D. O. North devised the matched falter for the optimum delection of a known signal in additive white noise. A similar result was obtained in 1946 independently by J. H. Van Vleck and D. Middleton, who coined the term matched falter.

In 1947, the geometric representation of signals was developed by V. A. Kotelnikovin a doctoral dissertation presented before the Academic Council of the Molotov Energy Insititute in Moscow. This method was subsequently brought to full fruition by John M.Wozencraft and Irwin M. Jacobs in a landmark textbook published in 1965.

In 1948, the theoretical foundations of digital communications were laid by Claude Shannon in a paper entitled 'A Mathematical Theory of Communication.' Shannons paper was received with immediate and enthusiastic acclaim. It was perhaps this response that emboldened Shannon to amend the title of his paper to 'The Mathematical Theory of Communication' when it was reprinted a year later in a book co-authored with Warren Weaver. It is noteworthy that prior to the publication of Shannons 1948 classic paper, it was believed that increasing the rate of information transmission over a channel would increase the probability of error; the communication theory community was taken by surprise when Shannon proved that this was not true, provided that the transmission rate was below the channel capacity. Shannons 1948 pap

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