Bell and the Telephone
As Edison was beginning his work at Menlo Park, the telephone made its first public appearance at the Philadelphia Centennial Fair on June 25, 1876. Its inventor, Alexander Graham Bell, envisioned a network of telephones that would enable any person to reach any other person in the world instantly. Bell’s ambition has yet to be fully realized but in the twentieth century the telephone became indispensable to daily life in the United States. Before the phone, voice communication was limited to distances measured in feet. Telegraph messages traveled longer distances but had to be encoded and decoded by operators at each end. With a telephone, communication was direct, and no place on the network was more than a simple phone call from any other place on it.
Bell did not set out to invent a telephone; his original goal was to invent a better telegraph. But he soon realized that his approach to telegraphy might make voice communication possible. After patenting his telephone and then demonstrating it, he formed a company to provide telephone service and then retired from the business. As the network grew, it encountered technical difficulties, principally the attenuation or weakening of calls over longer distances. To overcome this challenge, the Bell System turned to more scientifically trained engineers, who achieved long-distance telephony and met the growing need for carrying capacity as the number of telephone subscribers grew.
Bell to Boston
Born in Edinburgh, Scotland, Alexander Graham Bell (1847–1922) grew up with the ambition to follow the profession of his father, Alexander Melville Bell (1819–1905), a well-known speech teacher at the University of Edinburgh.1 Melville Bell’s invention of “visible speech” taught deaf people how to communicate vocally (figure 3.1a and b).2 Using this approach, his three sons worked with him as teachers of the deaf. The middle son, Alexander Graham, also took an interest in the mechanics of sound. He found that he could produce vowel sounds with tuning forks, and he learned of an experiment in which the German scientist Hermann von Helmholtz had used the magnetic field of an electric current to resonate tuning forks. Bell mistakenly believed Helmholtz had demonstrated that sound could be carried by electricity. But the misunderstanding encouraged Bell to pursue the idea that speech might be carried by an electric current.3
Figure 3.1a. Alexander Melville Bell. Source: Alexander Melville Bell, English Visible Speech and Its Typography Elucidated (Washington, DC: Volta Bureau, 1904), frontispiece.
Figure 3.1b. Title page of Bell’s book on visible speech. Source: Alexander Melville Bell, English Visible Speech and Its Typography Elucidated (Washington, DC: Volta Bureau, 1904).
Melville Bell’s first and third sons died of tuberculosis as young men, and the failing health of Alexander Graham prompted the family to move to Canada in 1870. The Bells settled in Brantford, Ontario, seventy-five miles west of Niagara Falls. The younger Bell soon recovered and accepted an invitation to teach at a school for the deaf in Boston, Massachusetts, where he arrived in April 1871. His success teaching deaf students to communicate soon attracted notice. In the fall of 1873, he joined the faculty of the newly founded Boston University as a professor of vocal physiology. To save money, he moved to Salem, just outside the city, where he lived with the family of Thomas Sanders, a merchant. Bell taught his deaf son, George Sanders, in return for room and board and commuted to his teaching in Boston.
America’s first integrated textile factories had begun outside Boston in the 1820s, and by the 1870s the city was a leading center of telegraph research. The wealth of its industry had enhanced the city’s role as a great center of learning, with Harvard College and the newer institutions of Boston University and the Massachusetts Institute of Technology in the forefront. An invitation to lecture at MIT on visible speech and a tour of the school’s laboratories renewed Bell’s earlier interest in the relationship between electricity and sound.4 In the spring of 1875 he reduced his teaching (and his income) in order to devote more time to private research (figure 3.2).
From Telegraph to Telephone
The discovery of electromagnetism in the early nineteenth century prompted some researchers to investigate its possible use in telecommunication. In 1830 the physicist Joseph Henry demonstrated how electricity and magnetism could be employed to transmit a signal. Henry wrapped an insulated copper wire around an iron U-shaped electromagnet. Inside the arms of the magnet stood one end of a permanently magnetized steel bar on a pivot. When Henry closed the wire circuit, sending battery current around the magnet, the magnetic force pulled the inside end of the steel bar. The outside end of the bar swiveled and struck a bell (sidebar 3.1).5
Henry saw his bell experiment as a way to demonstrate a scientific principle; he had no interest in its practical use for communication. The development of a practical telegraph was the work of Samuel F. B. Morse (1791–1872), who devised an electric circuit powered by batteries (sidebar 3.1). Pressing a sender key interrupted the flow of current, causing a printer on the receiving end to print in a code of dots and dashes that Morse devised to transmit information. Morse patented his telegraph in 1840 and demonstrated it in 1844 over a line erected by Ezra Cornell from Baltimore to Washington. Telegraph companies soon began wiring the United States under license from Morse. Cornell helped found Western Union, which became the dominant U.S. telegraph company after the Civil War. As telegraphy spread, operators found that they could transmit messages faster if the signal activated a sounder instead of a printer.6
Figure 3.2. Alexander Graham Bell, circa 1875. Courtesy of AT&T Archives, Warren, NJ. No. H-1/8. Property of AT&T Archives. Reprinted by permission of AT&T.
Henry and Electromagnetism
The Morse Telegraph
During the mid-nineteenth century, as railways and steamships brought the world closer together, electric telegraphy over land lines and undersea cables provided nearly instantaneous transmission of news and messages. By the 1870s, however, the volume of telegraph traffic had grown so much that congestion had become a serious problem. Engineers began looking for ways to multiplex messages, to send more than one message over the same line at the same time. In 1872 Joseph Stearns of Boston patented a “duplex” telegraph with the ability to send a message in each direction simultaneously, while Thomas Edison developed a “quadruplex” system in 1874 that could transmit two messages in each direction over a single line at once.7 Fortune appeared to await inventors who could send even more messages. Alexander Graham Bell began his career as an inventor by joining the search for a better multiplex telegraph.
Bell’s approach reflected his interest in hearing and sound. He knew that the human eardrum vibrated to sounds carried through the air. He also knew that the magnetic field of an electric current could vibrate a tuning fork and produce sound. He wondered if sound could be carried by an electric current. When current activated an electromagnet, a magnetic field or flux formed around the magnet. Bell’s idea was to place a tuned steel reed close to an electromagnet and tap it. The vibrating reed would vary the magnetic flux, and, in so doing, vary the electric current as well. He believed that the current would transmit the variation to the flux of a distant electromagnet on the same circuit, and an adjacent steel reed tuned to the same frequency would then sound (sidebar 3.2). With a set of tuned reeds at one end, Bell hoped that he could send multiple messages over a single line at the same time to a set of duplicate reeds at the other end. The vibrations would combine for transmission. If the receiving reeds could separate them, by each vibrating to one tone, a large number of messages could be sent and received simultaneously.8
To develop a “harmonic” telegraph, Bell needed financial backing. In 1873, at the invitation of Gardiner Hubbard, a prominent Boston attorney, Bell had begun to teach Hubbard’s deaf sixteen-year-old daughter, Mabel (figure 3.3a, b). Hubbard, who had a keen interest in telegraphy, opposed the monopoly of Western Union on long-distance communication. Bell’s idea promised a way to send more messages less expensively.9 Together with Thomas Sanders, Hubbard formed a partnership with Bell in February 1875 to support the latter in the development of a harmonic telegraph. Bell agreed to give all three joint ownership of the patent rights. To help him in his research, he found a capable technician, Thomas A. Watson, from the workshop of Charles Williams in Boston, where Thomas Edison had also had equipment made.10
From Mechanical Action to Mechanical Resonance
Multiplexing: Many Messages at Once
Figure 3.3a. Gardiner Hubbard. Courtesy of AT&T Archives, Warren, NJ. No. 95-1029. Property of AT&T Archives. Reprinted by permission of AT&T.
Figure 3.3b. Mabel Hubbard. Courtesy of AT&T Archives, Warren, NJ. No. 88-200499. Property of AT&T Archives. Reprinted by permission of AT&T.
Bell found that he could not tune his harmonic telegraph precisely enough to eliminate mutual interference of the reeds with each other at the receiving end. His difficulty prompted him to think more deeply about electricity and sound. The advantage of his idea was its use of varying frequencies and amplitudes to transmit information without interrupting the current. He believed that more signals in Morse code could travel in this way at a given time than as interruptions in the current. Bell soon realized that a continuous current was poorly suited to sending messages in a code of stops and starts. A continuous current that conveyed varying frequencies and amplitudes was ideally suited, however, to carrying the human voice (sidebar 3.3).
Earlier inventors had tried to use an electric current for telephony without fully understanding the need for the current to be continuous. In 1861 Philip Reis in Germany placed a metal surface or diaphragm at each end of a telegraph line. Speaking onto the diaphragm vibrated it, and the receiving metal surface reproduced the frequency (high or low tone) of the sound at the other end. But the Reis telephone circuit only closed when the diaphragm vibrated. It acted like a telegraph, in stops and starts, and could not transmit changes in the amplitude (intensity or loudness) of the sound.11 Bell understood that a telephone needed to transmit varying amplitudes as well as frequencies to carry intelligible speech and that to do so required an uninterrupted current. Bell received encouragement from Joseph Henry, who had served as the secretary of the Smithsonian Institution since 1846. The almost eighty-year-old Henry met the twenty-eight-year-old Bell in March 1875 and listened to his idea of using an “undulatory” electric current to carry voice. “You have the germ of a great invention,” Henry said. When Bell confessed his need for more knowledge about electromagnetism, Henry told him firmly, “Get it.”12 Bell redoubled his study.
A breakthrough finally came on June 2, 1875. While testing the reeds of a harmonic telegraph, Bell and Watson found that one of the reeds didn’t sound, so they turned off the battery current. Thinking it was stuck, Watson plucked the reed. Enough residual magnetism was in the circuit to cause a receiving reed to sound in another room where Bell heard it. The sound was not the normal tone of the receiving reed. Bell realized with excitement that the circuit had transmitted a new sound. The next day, he spoke onto a diaphragm connected to a reed and failed to produce speech in an identical receiver in another room. But he was now convinced that he was on the right track.13
Frequency and Amplitude
From Intermittent Taps to Continuously Varying Tones
Hubbard and Sanders disapproved of Bell’s interest in telephony, which they regarded as a distraction. There was a proven market, in their view, only for a new kind of telegraph. To complicate matters, Bell began to realize that his feelings toward his deaf student, Mabel Hubbard, were changing from teacher to suitor. At age twenty-eight he was eleven years older, and her parents objected. But on August 26 Bell had a meeting with Mabel and believed that all was not lost. Just before Thanksgiving, Gardner Hubbard demanded that Bell concentrate on telegraphy or lose contact with Mabel. Mabel settled the issue on Thanksgiving Day, her eighteenth birthday, by declaring her love for Bell and asking her father for the engagement. Hubbard eventually accepted both the potential son-in-law and his telephone.14
On January 20, 1876, Bell notarized a patent application that Hubbard’s attorneys in Washington, DC, filed on February 14. The Patent Office granted the claim on March 7, 1876, as Patent No. 174,465. This patent, the first of his two telephone patents, consisted of two pages of drawings and four pages of accompanying text. Bell argued that a conventional telegraph line had a limit to the number of messages it could carry at any one time with an interrupted current. He then explained how a harmonic telegraph and a continuous undulatory current would overcome this problem. Then he noted: “I desire here to remark that there are many other uses to which these instruments may be put, such as the simultaneous transmission of musical notes, differing in loudness as well as in pitch, and the telegraphic transmission of noises or sounds of any kind.” Bell then outlined his revolutionary idea, a telephone, almost as an afterthought, and claimed for it the ability to transmit the human voice.15
Bell’s demonstration at the Philadelphia Centennial in June 1876 drew national attention to his invention, and over the following year he lectured widely on it (figure 3.4). On July 9, 1877, Hubbard, Bell, Sanders, and Watson formed the Bell Telephone Company, and two days later Bell and Mabel Hubbard were married.
Figure 3.4. Bell’s 1877 lecture in Salem, Massachusetts. Source: Scientific American, 36:13 (March 31, 1877): 191.
Figure 3.5. Elisha Gray. Courtesy of AT&T Archives, Warren, NJ. No. W11-1. Property of AT&T Archives. Reprinted by permission of AT&T.
Bell, Gray, and Edison
Soon after filing his patent application, Bell learned that a rival inventor had filed a provisional claim (called a caveat) for a telephone later the same day, February 14, 1876. The rival was Elisha Gray (1835–1901), a telegraph engineer (figure 3.5). In 1872 Gray had cofounded the Western Electric Company in Chicago, which soon became the principal supplier of telegraph equipment to Western Union. Gray was working on a harmonic telegraph at the same time as Bell. At the time of his caveat, Gray did not have a working telephone (neither did Bell), but he did have a different idea for a phone.16
According to Ohm’s Law, in an electric circuit, voltage equals current times resistance, V = IR. Bell’s telephone varied the current (I) by changing its magnetic flux in order to carry voice. In his telephone, Gray varied the current instead by changing the resistance (R) of the circuit (sidebar 3.4). In Gray’s transmitter, a horizontal diaphragm had a short vertical length of wire suspended from it below. The vibrations from speaking onto the diaphragm caused the wire to dip up and down in a glass of sulfuric acid and water, which varied the resistance of an electric circuit that went through the diluted acid. The circuit carried the disturbance in the current to a receiver with an electromagnet and a diaphragm, which reproduced the original sound.
Bell was aware that variable resistance could also carry sound over an electric circuit, although his telephone design did not use the principle.17 Bell and Watson built and tested a “liquid” telephone similar to Gray’s in March 1876, and it was into this phone that Bell spoke the first words to be carried by telephone: “Mr. Watson—come here—I want to see you.”18 A liquid telephone was obviously impractical and in his Centennial telephone Bell returned to his original idea of varying the current electromagnetically. In a second patent filed in January 1877, however, Bell claimed more broadly as his discovery the use of an undulating current to carry voice and musical tones, not the particular mechanism of transmitting such a current.19
In 1875, after learning of the Reis telephone, Thomas Edison had explored the idea of a telephone by varying the resistance. But like other engineers working in telegraphy, he saw telephony as a mere curiosity. In a telegraph caveat filed in January 1876, he claimed a way to transmit sound but did not claim the ability to carry voice. Prompted by Bell’s Centennial demonstration, Edison found a more practical way to vary the resistance than Gray’s liquid telephone. In 1877 Edison patented a new telephone transmitter in which the pressure of speaking onto a diaphragm over a small bed of solid carbon, through which an electric current passed, varied the resistance and carried the tones of the human voice more clearly than Bell’s telephone.20
Gray and Edison sold their telephone patents to Western Union, which began to produce telephones of its own, prompting the Bell Telephone Company to sue for patent infringement. However, the two companies reached a settlement on November 10, 1879. Telephones at the time could send calls only a distance of about twenty miles and Western Union did not see a threat to its established telegraph business. The company was more worried about a threat to its long-distance telegraph monopoly from a group (which soon fell apart) led by the financier Jay Gould. In the settlement, Western Union gave up its claims to the telephone and agreed to share its patents and equipment with Bell Telephone. In return, Western Union received a percentage of the Bell company’s receipts over the following seventeen years in which its patent protection would remain in force.21
Bell’s Telephone
Gray’s Telephone
Not wanting to manage a business, Bell resigned from his company’s board of directors in 1879 and soon left the company altogether. He and Mabel sold their stock over the next four years to retire as modest millionaires. The other original partners also sold their shares early. As a result, the telephone never produced an owner or group of owners who became as wealthy as Rockefeller, Carnegie, and other industrialists of the period. The high point of Bell’s career ended, and he lived comfortably and famously until his death in August 1922; Mabel died five months after him.22
Achieving Long Distance
The first telephones connected directly to each other, but such interconnections quickly became impractical as the number of phones in use grew. Instead, phone lines went to a local exchange office, where operators connected subscribers to other phones connected to the same office. Eventually, local exchanges connected to each other through trunk lines. Automatic switching systems appeared in the 1880s, but customers preferred human contact and operators continued to handle most calls (figure 3.6). But the telephone network had to overcome two barriers to its growth, one managerial and the other technical, in order to become a nationwide system.
To manage the new company, Gardiner Hubbard hired Theodore N. Vail (1845–1920), a younger cousin of Alfred Vail (1807–1859), who had helped Samuel F. B. Morse develop the telegraph. Theodore Vail had worked as a railway telegrapher and later managed the railway mail service for the U.S. Post Office. Upon joining the Bell company, he expanded the telephone network by encouraging local phone companies to organize under license, with the Bell firm taking part ownership of each company. In 1881, Vail bought a controlling interest in Western Electric, which manufactured telephone equipment for the Bell System. He also improved transmission distances by replacing the steel wires of the network with more conductive copper wires. In 1885 he formed a long-distance subsidiary, American Telephone and Telegraph (AT&T), which absorbed the original Bell company in 1899. However, Vail’s drive to invest in capacity rather than reap short-term profits brought him into conflict with new investors, and he resigned in 1887. With the expiration of the second Bell patent in 1894, independent companies began to compete with the Bell System. Telephone ownership surged in the 1890s and the company began to lose its share of the market.23
Figure 3.6. Telephone operators in 1895. Source: Cassier’s Magazine, 8:1 (May 1895): 15.
The Bell company realized that it would need to innovate to preserve its still-dominant position; and it did so by overcoming the technical barriers to long-distance calling. Even over copper wires, the strength of calls attenuated from resistance in the lines, with the loss per mile roughly proportional to the resistance. Increasing the cross-sectional area of the copper wire would reduce line resistance but add substantially to the cost of the lines. Wires separated from each other on telephone poles could transmit calls only about one thousand miles, but wires bundled together in underground cables (used mainly in congested areas) had only a fraction of this range.24
Figure 3.7. George Campbell. Source: Collected Papers of George Ashley Campbell (New York: American Telephone and Telegraph, 1937), frontispiece. Reprinted by permission of AT&T.
To overcome the limitation on long-distance calls and to improve the reach of cables, AT&T turned to engineers with more advanced scientific and mathematical training. In 1897 the company hired George Campbell (1870–1954), a civil engineering graduate of the Massachusetts Institute of Technology who had taken a master’s degree in physics from Harvard and had studied in Europe (figure 3.7). Campbell was aware of the new scientific research in Europe on electromagnetism and wave propagation that led to the development of radio (see chapter 7). He also knew of research that suggested a solution to the problem of long-distance telephony.25
A circuit can store electricity and magnetism as well as conduct and resist electric current. Electricity is stored as negative or positive charge and the capacity of a circuit to store electric charge is its capacitance. The capacity to store magnetism is its inductance. Based on earlier experience with telegraphy, Bell engineers had assumed that attenuation of a phone call was proportional to the product of resistance and capacitance in the line. But the British physicist Oliver Heaviside argued that this rule neglected inductance and that adding inductance to a telephone line would be equivalent to reducing resistance. Following this idea, Campbell placed coils at intervals along a line to add inductance, and experiments found that the added inductance gave long-distance calls greater strength and clarity. Campbell had to place iron cores inside the coils to achieve the desired strength and he had to solve the problem of how far apart to space them. But with these adjustments, the Bell System began to employ inductive loading, as the technique was called, in 1902. The new technique doubled the range of long-distance calls on open wires and tripled it over cables.26
A physics professor at Columbia University, Michael Pupin (1858–1935), was working independently on the problem of attenuation, and he patented a version of inductive loading in 1900 just ahead of Campbell. AT&T purchased Pupin’s patent rights to keep the innovation away from competitors.27 Adjusting the electrical properties of the line to compensate for a weak signal was not easy, though, and adding inductance did not make possible full transcontinental telephone calling. A better alternative appeared in 1907, when the radio engineer Lee de Forest invented the triode, an electronic amplifier (see chapter 7). Amplifiers could renew the electrical energy in a call as many times as needed to travel any distance desired. With amplifiers, transcontinental calls finally became practical, as Bell and Watson demonstrated when they emerged from retirement to make the first one in 1915 between New York and San Francisco.28
As demand for service grew, the telephone system (like the telegraph network before it) eventually needed a way to send more than one call over the same line at the same time. The telephone industry ironically returned to the principle that Alexander Graham Bell had tried to make practical in his harmonic telegraph, the principle of frequency multiplexing. By 1918 Bell System engineers had found a way to transmit multiple calls over a single line at the same time by giving each call a different electromagnetic frequency range. George Campbell’s 1909 invention of the wave filter made it possible to separate these frequencies clearly at each end.29
The telephone served a predominantly business clientele in the 1880s and 1890s. The focus of the technology changed, however, as people began to use it for social purposes, and for those who had it, telephone service became a vital part of daily life (figure 3.8). As the cost of service fell in the twentieth century, telephone use spread and gave Americans the means to communicate almost instantly. In 1907, ownership of AT&T passed from Boston to new investors in New York, and Theodore Vail returned to head the company until 1919. The Bell System became a telecommunications monopoly in 1911 when it acquired its former rival Western Union. When the federal government threatened to break up the Bell System, however, AT&T agreed in 1913 to divest itself of Western Union and allow competing telephone companies access to its long-distance telephone network. The system functioned as a quasi-public utility until its breakup in 1984.30
Alexander Graham Bell often called himself a scientist and he associated with prominent scientists in his later life,31 but Bell was always primarily an engineer. He came to the telephone after joining the search for a better telegraph and he succeeded because those inventors with more experience in telegraph engineering did not recognize the importance of telephony as readily as an outsider like Bell, whose experience lay in human hearing and speech. Electrical engineers in the 1870s were oriented toward the telegraph industry and its incremental needs, which promised the greatest rewards to innovators. Gray himself did not recognize the value of the telephone until Bell was able to commercialize it; and even Edison, in his initial view of the telephone, thought much more as a telegraph engineer than as the visionary he soon proved himself in the field of electric power and lighting.32 Bell had begun his research in the hope of developing an improved telegraph and his backers had originally demanded that he produce such a device—and not distract himself with telephony. His insight was to see the value of an undulatory current to carry speech.
As the telephone network grew, though, its own needs became more complex. The industry began to need the assistance of engineers with more advanced training in mathematics and science to improve the technology and overcome the obstacles to its expansion. Campbell’s adding of inductance to the lines was a clear case of applying a scientific principle to meet an engineering need. But inductive loading was not the only scientifically possible answer to the problem of reducing attenuation. Bell engineers could have increased the cross-sectional area of the copper wires, as Edison could have done to reduce power losses in his transmission lines. Like Edison, the Bell engineers chose not to add cross-sectional area to the lines because of the high cost. Inductive loading came into use because scientific constraints left room for engineering choice. Engineering judgment also proved crucial in another key industry at the turn of the century, the chemical process industry of petroleum refining.
Figure 3.8. King Harris (age three) and his brother Lawrence (age five) in San Francisco speaking with their parents in Washington, DC., in 1916. Source: National Geographic Magazine, 29:3 (March 1916): 301.
