Invention of the telephone

An actor portraying Bell speaking into a early model of the telephone

The modern telephone is the culmination of work done by many individuals and the history of the invention of the telephone is a very confusing collection of claims and counterclaims, made no less confusing by the many lawsuits which attempted to resolve the patent claims of several individuals. This article covers the early years 1844-1898, from conception of the idea of an electric voice-transmission device, failed attempts to use "make-and-break" current, successful experiments with electromagnetic devices by Alexander Bell and Thomas Watson, to commercially successful telephones in the late 19th century. This is a summary of the attempts, success and failures of individual inventors during that half century.

The story begins with a non-electrical string telephone or "lover's telephone" that has been known for centuries, comprising two diaphragms connected by a taut string or wire. Sound waves are carried as mechanical vibrations along the string or wire from one diaphragm to the other. The classic example is the tin can telephone, a children's toy made by connecting the two ends of a string to the bottoms of two metal cans, paper cups or similar items. The essential idea of this toy was that a diaphragm can collect voice sounds from the air, as in the ear, and can also transmit voice sounds through a string or wire for reproduction at a distance.

Telephone Pioneers

Charles Grafton Page

TOBY MCGOWAN INVENTED THE TELEPHONE Charles Grafton Page (1812-1868) in 1837 passed an electric current through a coil of wire placed between the poles of a horseshoe magnet. He observed that connecting and disconnecting the current caused a ringing sound in the magnet. He called this effect "galvanic music".

Innocenzo Manzetti

Main article: Innocenzo Manzetti

Innocenzo Manzetti considered the idea of a telephone as early as 1844, and may have made one in 1864, as an enhancement to an automaton built by him in 1849.

Charles Bourseul

Main article: Charles Bourseul

In 1854 Charles Bourseul, a French telegrapher, published a plan for conveying sounds and even speech by electricity in the magazine L'Illustration (Paris). Bourseul's ideas were also published in Didaskalia (Frankfurt am Main) on September 28, 1854: "Suppose", he explained, “that a man speaks near a movable disc sufficiently flexible to lose none of the vibrations of the voice; that this disc alternately makes and breaks the currents from a battery: you may have at a distance another disc which will simultaneously execute the same vibrations.... It is certain that, in a more or less distant future, speech will be transmitted by electricity. I have made experiments in this direction; they are delicate and demand time and patience, but the approximations obtained promise a favourable result."

This make-or-break signaling was able to transmit tones and some vowels, but since it did not follow the analog shape of the sound wave (the contact was pure digital, on or off) it could not transmit consonants, or complex sounds. Bourseul's phrase "make and break the current" was inaccurately applied to later work by Philipp Reis who successfully transmitted faint voice sounds with unbroken current.

Johann Philipp Reis

Main article: Johann Philipp Reis

In 1860 Johann Philipp Reis produced a device that could transmit musical notes, indistinct speech, and occasionally distinct speech. The first sentence spoken on it was "Das Pferd frisst keinen Gurkensalat" (the horse doesn't eat cucumber salad). In the Reis transmitter, a diaphragm was attached to a needle that pressed against a metal contact. This resembled the make-or-break design of Bourseul, although Reis used the term "molecular motion" (molekulare Bewegung) to describe the contact points of his transmitter. The Reis transmitter was very difficult to operate, since the relative position of the needle and the contact were critical to the device's operation. This can be called a "telephone", since it did transmit voice sounds over distance, but was hardly a commercially practical telephone in the modern sense, as it failed to reliably transmit a good copy of any supplied sound.#

Thomas Edison tested the Reis equipment and found that "single words, uttered as in reading, speaking and the like, were perceptible indistinctly, notwithstanding here also the inflections of the voice, the modulations of interrogation, wonder, command, etc., attained distinct expression."

Prior to 1947, the Reis device was tested by the British company Standard Telephones and Cables (STC). The results also confirmed it could faintly transmit and receive speech. At the time STC was bidding for a contract with Alexander Graham Bell's American Telephone and Telegraph Company, and the results were covered up by STC's chairman Sir Frank Gill to maintain Bell's reputation.

Antonio Meucci

Main article: Antonio Meucci

An early voice communicating device was invented around 1854 by Antonio Meucci, who called it a telettrofono. In 1871 Meucci filed a caveat at the US Patent Office. His caveat describes his invention, but does not mention a diaphragm, electromagnet, conversion of sound into electrical waves, conversion of electrical waves into sound, or other essential features of an electromagnetic telephone.

The first American demonstration of Meucci's invention took place in Staten Island, New York in 1854. In 1860, a description of it was reportedly published in an Italian-language New York newspaper, although no known copy of that newspaper issue or article survived to the present day. Meucci claimed to have invented a paired electro-magnetic transmitter and receiver, where the motion of a diaphragm modulated a signal in a coil by moving an electromagnet, although this was not mentioned in his 1871 U.S. patent caveat. A further discrepancy observed was that the device described in the 1871 caveat employed only a single conduction wire, with the telephone's transmitter-receivers being insulated from a 'ground return' path.

In the 1880s Meucci was credited with the early invention of inductive loading of telephone wires to increase long-distance signals. Unfortunately, serious burns from an accident, a lack of English, and poor business abilities resulted in Meucci failing to develop his inventions commercially in America. Meucci demonstrated some sort of instrument in 1849 in Havana, Cuba, but the evidence is clear that this was not an electromagnetic telephone and may have been a variant of a string telephone that used wire. Meucci has been further credited with invention of an anti-sidetone circuit. However, examination showed that his solution to sidetone was to maintain two separate telephone circuits, and thus use twice as many transmission wires. The anti-sidetone circuit later introduced by Bell Telephone instead cancelled sidetone through a feedback process.

An American District Telegraph (ADT) laboratory reportedly lost some of Meucci's working models, his wife reportedly disposed of others and Meucci, who sometimes lived on public assistance, chose not to renew his 1871 teletrofono patent caveat after 1874.

Meucci was recognized for his pioneering work on the telephone by the United States House of Representatives in 2002. The resolution stated that "if Meucci had been able to pay the $10 fee to maintain the caveat after 1874, no patent could have been issued to Bell." No such patent could have issued to Bell in March 1876. If Meucci had renewed his caveat, he would have been given an opportunity to prove to the examiner that the device described in his caveat was the electromagnetic telephone described in Bell's patent application.

The Meucci resolution by the US Congress was promptly followed by a Canada legislative motion by Canada's 37th Parliament, declaring Alexander Graham Bell as the inventor of the telephone. Others in Canada disagreed with the Congressional resolution, some of whom provided criticisms of both its accuracy and intent.

Further information: [[:Canadian Parliamentary Motion on Alexander Graham Bell]]

Chronology of Meucci's invention

An Italian researcher in telecommunications, engineer Basilio Catania, and the Italian Society of Electrotechnics, "Federazione Italiana di Elettrotecnica", have devoted a Museum to Antonio Meucci, constructing a chronology of his invention of the telephone and tracing the history of the two legal trials involving Meucci and Alexander Graham Bell. Both claim that Meucci was the real inventor of the telephone, and base their argument on the reconstructed evidence. What follows, if not otherwise stated, is a résumé of their historic reconstruction.

• In 1834 Meucci constructed a kind of acoustic telephone as a way to communicate between the stage and control room at the theatre "Teatro della Pergola" in Florence. This telephone is constructed on the model of pipe-telephones on ships and is still working.
• In 1848 Meucci developed a popular method of using electric shocks to treat rheumatism. He used to give his patients two conductors linked to 60 Bunsen batteries and ending with a cork. He also kept two conductors linked to the same Bunsen batteries. He used to sit in his laboratory, while the Bunsen batteries were placed in a second room and his patients in a third room. In 1849 while providing a treatment to a patient with a 114V electrical discharge, in his laboratory Meucci heard his patient's scream through the piece of copper wire that was between them, from the conductors he was keeping near his ear. His intuition was that the "tongue" of copper wire was vibrating just like a leave of an electroscope; which means that there was an electrostatic effect. In order to continue the experiment without hurting his patient, Meucci covered the copper wire with a piece of paper. Through this device he heard inarticulated human voice. He called this device "telegrafo parlante" (litt. "talking telegraph").
• On the basis of this prototype, Meucci worked on more than 30 kinds of sound transmitting devices inspired by the telegraph model as did other pioneers of the telephone, such as Charles Bourseul, Philipp Reis, Innocenzo Manzetti and others. Meucci later claimed that he did not think about transmitting voice by using the principle of the telegraph "make-and-break" method, but he looked for a "continuous" solution that did not interrupt the electric current.
• In 1856 Meucci later claimed that he constructed the first electromagnetic telephone, made of an electromagnet with a nucleus in the shape of a horseshoe bat, a diaphragm of animal skin, stiffened with potassium dichromate and keeping a metal disk stuck in the middle. The instrument was hosted in a cylindrical carton box. He said he constructed this as a way to connect his second-floor bedroom to his basement laboratory, and thus communicate with his wife who was an invalid.
• Meucci separated the two directions of transmission in order to eliminate the so-called "local effect", adopting what we would call today a 4-wire-circuit. He constructed a simple calling system with a telegraphic manipulator which short-circuited the instrument of the calling person, producing in the instrument of the called person a succession of impulses (clicks), much more intense than those of normal conversation. As he was aware that his device required a bigger band than a telegraph, he found some means to avoid the so-called "skin effect" through superficial treatment of the conductor or by acting on the material (copper instead of iron). He successfully used an insulated copper plait, thus anticipating the litz wire used by Nikola Tesla in RF coils.
• In 1864 Meucci later claimed that he realized his "best device", using an iron diaphragm with optimized thickness and tightly clamped along its rim. The instrument was housed in a shaving-soap box, whose cover clamped the diaphragm.
• In August 1870, Meucci later claimed that he obtained transmission of articulate human voice at a mile distance by using as a conductor a copper plait insulated by cotton. He called his device "teletrofono". Drawings and notes by Antonio Meucci dated September 27, 1870 show coils of wire on long distance telephone lines. The painting made by Nestore Corradi it:Nestore Corradi in 1858 mentions the sentence "Electric current from the inductor pipe"

The above information was published in the Scientific American Supplement No. 520, December 19, 1885, based on reconstructions produced in 1885, for which there was no contemporary pre-1875 evidence. Meucci's 1871 caveat did not mention any of the telephone features later credited to him by his lawyer, and which were published in that Scientific American Supplement, a major reason for the loss of the 'Bell v. Globe and Meucci' patent infringement court case, which was decided against him. See Antonio Meucci – Patent caveat, for the full printed text of his 1871 teletrofono patent caveat.

Cromwell Varley

Around 1870 Mr. C. F. Varley, F.R.S., a well-known English electrician, patented a number of variations on the audio telegraph based on Reis' work. He never claimed or produced a device capable of transmitting speech, only pure tones.

Poul la Cour

Around 1874 Poul la Cour, a Danish inventor, experimented with audio telegraphs on a telegraph line between Copenhagen and Fredericia in Jutland. His experiment used a vibrating tuning-fork to interrupt the line current, which, after traversing the line passed through an electromagnet that acted upon the tines of another tuning-fork, making it resonate at the same pitch of the transmitting fork. Moreover, the hums were also recorded on paper by turning the electromagnetic receiver into a relay, which actuated a Morse code printer by means of a local battery. Again, la Cour made no claims of transmitting voice, only pure tones.

Daniel Drawbaugh

Daniel Drawbaugh, a bearded rustic tinkerer from Pennsylvania, claimed to have invented a telephone using a teacup as transmitter as early as 1867, and to have applied for a patent about 1880, but his case was dismissed in the 1880-88 legal challenge to Bell (see The Telephone Cases), and also in 1896.

Electro-magnetic transmitters and receivers

Elisha Gray

Main article: Elisha Gray, See also: Elisha Gray and Alexander Bell telephone controversy

Elisha Gray, of Highland Park, Illinois (near Chicago) also devised a tone telegraph of this kind about the same time as La Cour. In Gray's tone telegraph, several vibrating steel reeds tuned to different frequencies interrupted the current, which at the other end of the line passed through electromagnets and vibrated matching tuned steel reeds near the electromagnet poles. Gray's 'harmonic telegraph,' with vibrating reeds, was used by the Western Union Telegraph Company. Since more than one set of vibration frequencies — that is to say, more than one musical tone — can be sent over the same wire simultaneously, the harmonic telegraph can be utilised as a 'multiplex' or many-ply telegraph, conveying several messages through the same wire at the same time. Each message can either be read by an operator by the sound, or from different tones read by different operators, or a permanent record can be made by the marks drawn on a ribbon of travelling paper by a Morse recorder. On 27 July 1875, Gray was granted U.S. patent 166,096 for "Electric Telegraph for Transmitting Musical Tones" (the harmonic telegraph).

On 14 February 1876, Gray filed a patent caveat for a telephone on the very same day in 1876 as did Bell's lawyer. The water transmitter described in Gray's caveat was strikingly similar to the experimental telephone transmitter tested by Bell on March 10, 1876, a fact which raised questions about whether Bell (who knew of Gray) was inspired by Gray's design or vice versa. Although Bell did not use Gray's water transmitter in later telephones, evidence suggests that Bell's lawyers may have obtained an unfair advantage over Gray.

Alexander Graham Bell

Main article: Alexander Graham Bell

Bell's March 10, 1876 laboratory notebook entry describing his first successful experiment with the telephone.

Alexander Graham Bell is commonly credited as the inventor of the first practical telephone. The classic story of his crying out "Watson, come here! I want to see you!" is a well known part of American history. Bell was the first to obtain a patent, in 1876, for an "apparatus for transmitting vocal or other sounds telegraphically", after experimenting with many primitive sound transmitters and receivers. Bell was also an astute and articulate business man with influential and wealthy friends.

As Professor of Vocal Physiology at Boston University, Bell was engaged in training teachers in the art of instructing deaf mutes how to speak, and experimented with the Leon Scott phonautograph in recording the vibrations of speech. This apparatus consists essentially of a thin membrane vibrated by the voice and carrying a light-weight stylus, which traces an undulatory line on a plate of smoked glass. The line is a graphic representation of the vibrations of the membrane and the waves of sound in the air.

This background prepared Bell for work with spoken sound waves and electricity. He began his experiments in 1873-1874 with a harmonic telegraph, following the examples of Bourseul, Reis, Meucci, and Gray. Bell's designs employed various on-off-on-off make-break current-interrupters driven by vibrating steel reeds which sent interrupted current to a distant receiver electro-magnet that caused a second steel reed or tuning fork to vibrate.

During a June 2, 1875 experiment by Bell and his assistant Watson, a receiver reed failed to respond to the intermittent current supplied by an electric battery. Bell told Watson, who was at the other end of the line, to pluck the reed, thinking it had stuck to the pole of the magnet. Mr. Watson complied, and to his astonishment Bell heard a reed at his end of the line vibrate and emit the same timbre of a plucked reed, although there was no interrupted on-off-on-off current from a transmitter to make it vibrate. A few more experiments soon showed that his receiver reed had been set in vibration by the magneto-electric currents induced in the line by the motion of the distant receiver reed in the neighborhood of its magnet. The battery current was not causing the vibration but was needed only to supply the magnetic field in which the reeds vibrated. Moreover, when Bell heard the rich overtones of the plucked reed, it occurred to him that since the circuit was never broken, all the complex vibrations of speech might be converted into undulating (alternating) currents, which in turn would reproduce the complex timbre, amplitude, and frequencies of speech at a distance.

After Bell and Watson discovered on June 2, 1875 that movements of the reed alone in a magnetic field could reproduce the frequencies and timbre of spoken sound waves, Bell reasoned by analogy with the mechanical phonautograph that a skin diaphragm would reproduce sounds like the human ear when connected to a steel or iron reed or hinged armature. On July 1, 1875, he instructed Watson to build a receiver consisting of a stretched diaphragm or drum of goldbeater's skin with an armature of magnetized iron attached to its middle, and free to vibrate in front of the pole of an electromagnet in circuit with the line. A second membrane-device was built for use as a transmitter. This was the "gallows" phone. A few days later they were tried together, one at each end of the line, which ran from a room in the inventor's house in Boston to the cellar underneath. Bell, in the work room, held one instrument in his hands, while Watson in the cellar listened at the other. Bell spoke into his instrument, “Do you understand what I say?” and Mr. Watson answered “Yes”. However, the voice sounds were not distinct and the armature tended to stick to the electromagnet pole and tear the membrane.

Because of illness and other commitments, Bell made little or no telephone improvements or experiments for eight months until after his U.S. patent 174,465 was published.

Bell's success

Alexander Graham Bell's telephone patent drawing, 7 March 1876.

Bell's Prototype Telephone Centennial Issue of 1976

The first successful bi-directional transmission of clear speech by Bell and Watson was made on March 10, 1876 when Bell spoke into the device, “Mr. Watson, come here, I want to see you.” and Watson answered. Bell tested Gray's liquid transmitter design in this experiment, but only after Bell's patent was granted and only as a proof of concept scientific experiment to prove to his own satisfaction that intelligible "articulate speech" (Bell's words) could be electrically transmitted. Because a liquid transmitter was not practical for commercial products, Bell focused on improving the electromagnetic telephone after March 1876 and never used Gray's liquid transmitter in public demonstrations or commercial use.

Bell's telephone transmitter (microphone) consisted of a double electromagnet, in front of which a membrane, stretched on a ring, carried an oblong piece of soft iron cemented to its middle. A funnel-shaped mouthpiece directed the voice sounds upon the membrane, and as it vibrated, the soft iron “armature” induced corresponding currents in the coils of the electromagnet. These currents, after traversing the wire, passed through the receiver which consisted of an electromagnet in a tubular metal can having one end partially closed by a thin circular disc of soft iron. When the undulatory current passed through the coil of this electromagnet, the disc vibrated, thereby creating sound waves in the air.

This primitive telephone was rapidly improved. The double electromagnet was replaced by a single permanently magnetized bar magnet having a small coil or bobbin of fine wire surrounding one pole, in front of which a thin disc of iron was fixed in a circular mouthpiece. The disc served as a combined diaphragm and armature. On speaking into the mouthpiece, the iron diaphragm vibrated with the voice in the magnetic field of the bar-magnet pole, and thereby caused undulatory currents in the coil. These currents, after traveling through the wire to the distant receiver, were received in an identical apparatus. This design was patented by Bell on January 30, 1877. The sounds were weak and could only be heard when the ear was close to the earphone/mouthpiece, but they were distinct.

The first long distance telephone call was made on 10 August 1876 by Bell from the family homestead in Brantford, Ontario, to his assistant located in Paris, Ontario, some 10 miles (16 km) apart.

Public demonstrations

Earliest public demonstration of Bell's telephone

In June 1876, Bell exhibited a telephone prototype at the Centennial Exhibition in Philadelphia, where it attracted the attention of Brazilian emperor Pedro II and physicist and engineer Sir William Thomson, the 1st Baron Kelvin (best known as "Lord Kelvin"). In August 1876 at a meeting of the British Association for the Advancement of Science, Thomson revealed the telephone to the European public. In describing his visit to the Philadelphia Exhibition, Thomson said, 'I heard [through the telephone] passages taken at random from the New York newspapers: "s.s. Cox has arrived" (I failed to make out the s.s. Cox); "The City of New York", "Senator Morton", "The Senate has resolved to print a thousand extra copies", "The Americans in London have resolved to celebrate the coming Fourth of July!" All this my own ears heard spoken to me with unmistakable distinctness by the then circular disc armature of just such another little electro-magnet as this I hold in my hand.'

Later public demonstrations

The later telephone design was publicly exhibited on May 4, 1877 at a lecture given by Professor Bell in the Boston Music Hall. According to a report: Going to the small telephone box with its slender wire attachments, Mr. Bell coolly asked, as though addressing some one in an adjoining room, “Mr. Watson, are you ready!” Mr. Watson, five miles away in Somerville, promptly answered in the affirmative, and soon was heard a voice singing “America”. [...] Going to another instrument, connected by wire with Providence, forty-three miles distant, Mr. Bell listened a moment, and said, “Signor Brignolli, who is assisting at a concert in Providence Music Hall, will now sing for us.” In a moment the cadence of the tenor's voice rose and fell, the sound being faint, sometimes lost, and then again audible. Later, a cornet solo played in Somerville was very distinctly heard. Still later, a three-part song came over the wire from Somerville, and Mr. Bell told his audience “I will switch off the song from one part of the room to another, so that all can hear.” At a subsequent lecture in Salem, Massachusetts, communication was established with Boston, eighteen miles distant, and Mr. Watson at the latter place sang “Auld Lang Syne”, “The Star-Spangled Banner”, and “Hail Columbia”, while the audience at Salem joined in the chorus.

Summary of Bell's achievements

Bell did for the telephone what Henry Ford did for the automobile. Although not the first to experiment with telephonic devices, Bell and the companies founded in his name were the first to develop commercially practical telephones around which a successful business could be built and grow. Bell adopted carbon transmitters similar to Edison's transmitters and adapted telephone exchanges and switching plug boards developed for telegraphy. Watson and other Bell engineers invented numerous other improvements to telephony. Bell succeeded where others failed to assemble a commercially viable telephone system. It can be argued that Bell invented the telephone industry.

Variable resistance transmitters

Water microphone - Elisha Gray

Elisha Gray recognized the lack of fidelity of the make-break transmitter of Reis and Bourseul and reasoned by analogy with the lover's telegraph, that if the current could be made to more closely model the movements of the diaphragm, rather than simply opening and closing the circuit, greater fidelity might be achieved. Gray filed a patent caveat with the US patent office on February 14, 1876 for a liquid microphone. The device used a metal needle or rod that was placed — just barely — into a liquid conductor, such as a water/acid mixture. In response to the diaphragm's vibrations, the needle dipped more or less into the liquid, varying the electrical resistance and thus the current passing through the device and on to the receiver. Gray did not convert his caveat into a patent application until after the caveat had expired and hence left the field open to Bell.

When Gray applied for a patent for the variable resistance telephone transmitter, the Patent Office determined "while Gray was undoubtedly the first to conceive of and disclose the [variable resistance] invention, as in his caveat of 14 February 1876, his failure to take any action amounting to completion until others had demonstrated the utility of the invention deprives him of the right to have it considered."

Carbon microphone - Thomas Edison

Thomas Alva Edison took the next step in improving the telephone with his invention in 1878 of the carbon grain "transmitter" (microphone) that provided a strong voice signal on the transmitting circuit that made long-distance calls practical. Edison discovered that carbon grains, squeezed between two metal plates, had a variable electrical resistance that was related to the pressure. Thus, the grains could vary their resistance as the plates moved in response to sound waves, and reproduce sound with good fidelity, without the weak signals associated with electro-magnetic transmitters.

The carbon microphone was further improved by Emile Berliner, Francis Blake, David E. Hughes, Henry Hunnings, and Anthony White. The carbon microphone remained standard in telephony until the 1980s, and is still being produced.

Improvements to the early telephone

Additional inventions such as the call bell, central telephone exchange, common battery, ring tone, amplification, trunk lines, wireless phones, etc. were made by various engineers who made the telephone the useful and widespread apparatus it is now.

Telephone exchange - Tivadar Puskás

Tivadar Puskás was working on his idea for a telegraph exchange when Alexander Graham Bell received the first patent for the telephone. This caused Puskás to take a fresh look at his own work and he refocused on perfecting a design for a telephone exchange. Puskás got in touch with the American inventor Thomas Edison who liked the design. According to Edison, "Tivadar Puskas was the first person to suggest the idea of a telephone exchange". Puskás's idea finally became a reality in 1877 in Boston. It was then that the Hungarian word "hallom" "I hear you" was used for the first time in a telephone conversation when, on hearing the voice of the person at the other end of the line, Puskás shouted "hallom". This cannot be confirmed by any original documents, however it has passed into Hungarian modern folklore. Hallom was shortened to Hello, an older greeting that can be traced back to the Old English verb hǽlan.

Controversy

See also: Canadian Parliamentary Motion on Alexander Graham Bell

Further information: Elisha Gray and Alexander Bell telephone controversy

Bell has been widely recognized as the "inventor" of the telephone outside of Italy, where Meucci was championed as its inventor. In the United States, there are numerous reflections of Bell as a North American icon for inventing the telephone, and the matter was for a long time non-controversial. In June 2002, however, the United States House of Representatives passed a symbolic bill recognizing the contributions of Antonio Meucci "in the invention of the telephone" (not "for the invention of the telephone"), throwing the matter into some controversy. Ten days later the Canadian parliament countered with a symbolic motion conferring official recognition for the invention of the telephone to Bell.

Champions of Meucci, Manzetti, and Gray have each offered fairly precise tales of a contrivance whereby Bell actively stole the invention of the telephone from their specific inventor. In the 2002 congressional resolution, it was inaccurately noted that Bell worked in a laboratory in which Meucci's materials had been stored, and claimed that Bell must thus have had access to those materials. Manzetti claimed that Bell visited him and examined his device in 1865. And it is alleged that Bell bribed a patent examiner, Zenas Wilber, not only into processing his application before Gray's, but allowing a look at his rival's designs before final submission.

One of the valuable claims in Bell's 1876 U.S. patent 174,465 was claim 4, a method of producing variable electrical current in a circuit by varying the resistance in the circuit. That feature was not shown in any of Bell's patent drawings, but was shown in Elisha Gray's drawings in his caveat filed the same day, 14 February 1876. A description of the variable resistance feature, consisting of seven sentences, was inserted into Bell's application. That it was inserted is not disputed. But when it was inserted is a controversial issue. Bell testified that he wrote the sentences containing the variable resistance feature before 18 January 1876 "almost at the last moment" before sending his draft application to his lawyers. A book by Evenson argues that the seven sentences and claim 4 were inserted, without Bell's knowledge, just before Bell's application was hand carried to the Patent Office by one of Bell's lawyers on 14 February 1876.

Contrary to the popular story, Gray's caveat was taken to the US Patent Office a few hours before Bell's application. Gray's caveat was taken to the Patent Office in the morning of 14 February 1876 shortly after the Patent Office opened and remained near the bottom of the in-basket until that afternoon. Bell's application was filed shortly before noon on 14 February by Bell's lawyer who requested that the filing fee be entered immediately onto the cash receipts blotter and Bell's application was taken to the Examiner immediately. Late in the afternoon, Gray's caveat was entered on the cash blotter and was not taken to the Examiner until the following day. The fact that Bell's filing fee was recorded earlier than Gray's led to the myth that Bell had arrived at the Patent Office earlier. Bell was in Boston on 14 February and did not know this happened until later. Gray later abandoned his caveat and that opened the door to Bell being granted US patent 174465 for the telephone on 7 March 1876.

See also

• Timeline of the telephone
• History of the telephone
• The Telephone Cases –patent dispute and infringement court cases

Further reading

• Baker, Burton H. (2000), The Gray Matter: The Forgotten Story of the Telephone, Telepress, St. Joseph, MI, 2000. ISBN 0-615-11329-X
• Bell, Alexander Graham. (1911), Speech by Alexander Graham Bell, November 2, 1911: Historical address delivered by Alexander Graham Bell, November 2, 1911, at the first meeting of the Telephone Pioneers' Association, Beinn Bhreagh Recorder, November 1911, pp. 15-19;
• Bethure, Brian, (2008) Did Bell Steal the Idea for the Phone? (Book Review), Maclean's Magazine, February 4, 2008;
• Bourseul, Charles, Transmission électrique de la parole, L'Illustration (Paris), 26.08.1854 Template:Fr
• Bruce, Robert V. (1990), Bell: Alexander Bell and the Conquest of Solitude, Cornell University Press, 1990. ISBN 0-80149691-8
• Coe, Lewis (1995), The Telephone and Its Several Inventors: A History, McFarland, North Carolina, 1995. ISBN 0-7864-0138-9
• Evenson, A. Edward (2000), The Telephone Patent Conspiracy of 1876: The Elisha Gray - Alexander Bell Controversy, McFarland, North Carolina, 2000. ISBN 0-7864-0883-9
• Gray, Charlotte, (2006) "Reluctant Genius: The Passionate Life and Inventive Mind of Alexander Graham Bell", HarperCollins, Toronto, 2006, ISBN 0002006766, ISBN 9780002006767 IBO: 621.385092;
• Josephson, Matthew (1992), Edison: A Biography, Wiley, ISBN 0-471-54806-5
• Shulman, Seth, (2007) Telephone Gambit: Chasing Alexander Graham Bell's Secret, W.W. Norton & Comp.; 1st Edition, December 25, 2007), ISBN 0393062066, ISBN 978-0393062069
• Thompson, Sylvanus P. (1883), Philipp Reis, Inventor of the Telephone, London: E. & F. N. Spon, 1883.

External links

• Heroes of the Telegraph by John Munro at Project Gutenberg
• Alexander Bell's Experiments - the tuning fork and liquid transmitter.
• American Treasures of the Library of Congress, Alexander Graham Bell - Lab notebook I, pages 40-41 (image 22)
• Scientific American Supplement No. 520, December 19, 1885
• Telephone Patents

Patents

• US 161739  Transmitter and Receiver for Electric Telegraphs (tuned steel reeds) by Alexander Graham Bell (April 6, 1875)
• US 174465  Telegraphy (Bell's first telephone patent) by Alexander Graham Bell (March 7, 1876)
• US 178399  Telephonic Telegraphic Receiver (vibrating reed) by Alexander Graham Bell (June 6, 1876)
• US 181553  Generating Electric Currents (magneto) by Alexander Graham Bell (August 29, 1876)
• US 186787  Electric Telegraphy (permanent magnet receiver) by Alexander Graham Bell (January 15, 1877)
• US 201488  Speaking Telephone (receiver designs) by Alexander Graham Bell (March 19, 1878)
• US 213090  Electric Speaking Telephone (frictional transmitter) by Alexander Graham Bell (March 11, 1879)
• US 220791  Telephone Circuit (twisted pairs of wire) by Alexander Graham Bell (October 21, 1879)
• US 228507  Electric Telephone Transmitter (hollow ball transmitter) by Alexander Graham Bell (June 8, 1880)
• US 230168  Circuit for Telephone by Alexander Graham Bell (July 20, 1880)
• US 238833  Electric Call-Bell by Alexander Graham Bell (March 15, 1881)
• US 241184  Telephonic Receiver (local battery circuit with coil) by Alexander Graham Bell (May 10, 1881)
• US 244426  Telephone Circuit (cable of twisted pairs) by Alexander Graham Bell (July 19, 1881)
• US 250126 Speaking Telephone by Francis Blake (November 29, 1881)
• US 252576  Multiple Switch Board for Telephone Exchanges by Leroy Firman (Western Electric) (January 17, 1882)
• US 474230 Speaking Telegraph (graphite transmitter) by Thomas Edison (Western Union) May 3, 1892
• US 203016  Speaking Telephone (carbon button transmitter) by Thomas Edison
• US 222390  Carbon Telephone (carbon granules transmitter) by Thomas Edison
• US 485311 Telephone (solid back carbon transmitter) by Anthony C. White (Bell engineer) November 1, 1892
• US 597062  Calling Device for Telephone Exchange (dial) by A. E. Keith (January 11, 1898)
• US 687499 Telephone Transmitter (carbon granules "candlestick" microphone) by W.W. Dean (Kellogg Co.) November 26, 1901
• US 815176 Automatic Telephone Connector Switch (for rotary dial phones) by A E Keith and C J Erickson March 13, 1906