Relay history: talking telegraph

• Relay history
  
  • The method of "fast information transfer", or the origin of the relay
  • Distance recorder
  • Galvanism
  • Businessmen
  • But finally, the relay
  • Talking telegraph
  • Just connect
  • Forgotten generation of relay computers
  • Electronic era
• The history of electronic computers
  
  • Prologue
  • Colossus
  • ENIAC

The phone came about by chance. If the telegraph networks of the 1840s appeared thanks to a century-long study of the possibilities of transmitting messages by means of electricity, then people came across the phone in search of an improved telegraph. Therefore, it is quite easy to designate a plausible, though not entirely indisputable, date of the invention of the telephone - the year of the centenary of the founding of the United States, 1876.

And it cannot be said that the phone has no predecessors. Since 1830, researchers and researchers have been looking for ways to turn sound into electricity, and electricity into sound.

Electric sound

In 1837, Charles Page , a physician and experimenter on the field of electromagnetism from Massachusetts, came across a strange phenomenon. He placed an insulated coiled wire between the ends of the permanent magnet, and then each of the ends of the wire was lowered into a battery with mercury. Every time he opened or closed the circuit, raising the end of the wire from the tank or lowering it there, the magnet emitted a sound that could be heard from a distance of a meter. Paige called this galvanic music, and suggested that the whole thing is in the "molecular disorder" occurring in the magnet. Page launched a wave of research on two aspects of this discovery: the strange property of metallic materials to change shape when magnetized, and the more obvious generation of sound by electricity.

We are particularly interested in two studies. The first was conducted by Johann Phillip Reis. Reis taught mathematics and the exact sciences of schoolchildren at the Garnier Institute near Frankfurt, but in his spare time he did research on electricity. By that time, several electricians had already created new versions of galvanic music, but Reis was the first to master the alchemy of two-way translation of sound into electricity and back.

Reis realized that a diaphragm resembling a person’s eardrum could close and open an electrical circuit when vibrated. The first prototype of the “telephon” device [“long-range vehicle”], built in 1860, consisted of a carved “ear” with a membrane stretched on it made of a pig bladder. A platinum electrode was attached to the lower part of the membrane, which, when vibrated, opened and closed the circuit with the battery. The receiver was a coil of wire wound around a knitting needle attached to a violin. The body of the violin amplified vibrations of the needle-shaped shape when it was alternately magnetized and demagnetized.


Late Flight Model

Reis came up with a lot of improvements for the early prototype, and, along with other experimenters, found that if you sing or sing something into it, the sound transmitted remains recognizable. The words were harder to distinguish, and often they were distorted and became incomprehensible. Many messages about successful voice transfer used such common phrases as “good morning” and “how are you”, and they could be easily guessed. The main problem was that the Reis transmitter only opened and closed the loop, but did not regulate the power of the sound. As a result, it was possible to transmit only a frequency with a fixed amplitude, and this could not imitate all the subtleties of the human voice.

Reis believed that his work should be recognized by science, but did not achieve this. His device was a popular wonder among the scientific elite, and copies appeared in most of the centers of this elite: in Paris, London, and Washington. But his scientific work was rejected by Professor Poggendorff’s journal Annalen der Physik [the Annals of Physics], one of the oldest scientific journals and the most influential journal of the time. Reis' attempts to advertise the telephone with the help of telegraph companies also failed. He suffered from tuberculosis, and the worsening disease kept him from further serious research. As a result, in 1873, the disease took his life and ambitions. And this is not the last time this disease will prevent the development of the history of the phone.

While Reis was improving his phone, Hermann Ludwig Ferdinand Helmholtzdid the final touches to his fruitful study of auditory physiology: “The doctrine of auditory sensations as the physiological basis for the theory of music” [Die Lehre von den Tonempfindungen als physiologische Grundlage für die Theorie der Musik], published in 1862. Helmholtz, at that time a professor at the University of Heidelberg, was a giant of science of the 19th century, working on the physiology of vision, electrodynamics, thermodynamics, etc.

Helmholtz's work only casually relates to our history, but it is a pity to miss it. In the Doctrine of Auditory Sensations, Helmholtz did for music what Newton did for light — he showed how it would seem that a single sensation can be disassembled into its component parts. He proved that the differences in timbres, from the violin to the bassoon, comes only from the differences in the relative strength of their overtones (tones on a double, triple, etc., frequency with respect to the base note). But for our history, the most interesting thing about his work lies in a remarkable instrument that he developed for demonstration:


A variant of the Helmholtz synthesizer

The first device Helmholtz ordered in the workshop of Cologne. Simply put, it was a synthesizer capable of producing sounds based on a composition of simple tones. His most amazing opportunity was the inexplicable ability to reproduce vowel sounds that everyone is accustomed to hearing only coming from the human mouth.

The synthesizer worked from the beating of the main tuning fork, vibrating on the base note, closing and closing the circuit, immersing the platinum wire in a container with mercury. Eight magnetized tuning forks, each of which vibrated with its own overtone, rested between the ends of an electromagnet connected to a contour. Each loop circuit included electromagnets, and kept the tuning forks in a vibrating state. Next to each tuning fork was a cylindrical resonator capable of amplifying its humming to an audible level. In the normal state, the lid on the resonator was closed, and jammed the sound of the tuning fork. If you move the lid to the side, you could hear this overtone, and thus “play” the sound of a trumpet, piano or vowel “o”.

This device will play a small role in creating a new type of phone.

Harmonic Telegraph

One of the baits for inventors of the second half of the XIX century was multitelegraf. The more telegraph signals could be crammed into one wire, the greater was the efficiency of the telegraph network. By the early 1870s, several different methods of organizing duplex telegraphy were known (simultaneously sending two signals in opposite directions). Shortly thereafter, Thomas Edison improved them by creating a quadruplex, combining duplex and duplex (transmitting two signals in the same direction at the same time), so that the wire could be used four times more efficiently.

But was it possible to further increase the number of signals? Organize some octoroplex, or even more? The fact that sound waves could be turned into electric current and vice versa offered an interesting opportunity. What if you use tones of different heights to create an acoustic, harmonic, or, poetically speaking, musical telegraph? If the physical vibrations of different frequencies can be converted into electrical ones, and then reassembled into original frequencies on the other hand, then it would be possible to send multiple signals simultaneously without mutual interference. The sound itself would then be only a means to an end, an intermediate medium that forms currents so that several signals can exist in one wire. For simplicity, I will call this concept the harmonic telegraph,

This was not the only way to create multiplexed signals. In France, Jean-Maurice Emile Bodo [in whose honor the unit of symbolic velocity is named - baud / approx. perev.] by 1874 came up with a machine with a rotating distributor, alternately collecting signals from several telegraph transmitters. Now we would call it a multiplex with splitting by time, not by frequency. But this approach had a flaw - it would not have led to the creation of telephony.

By that time, Western Union dominated American telegraphy, which was formed in the 1850s in an attempt to eliminate unfavorable competition for all among several large telegraph companies - before the appearance of antitrust legislation, one could safely use such explanations to justify such mergers. One of the characters in our story described it as "probably the largest corporation ever to exist." Possessing thousands of kilometers of wires and spending huge amounts of money to build and support networks, Western Union followed with great interest developments in the field of multiplexed telegraphy.

Breakthrough in the telegraph business was waiting for another player. Gardiner Green HubbardBoston lawyer and entrepreneur was one of the main supporters of the transfer of the American telegraph to the control of the federal government. Hubbard believed that telegrams could be as cheap as letters, and he was determined to undermine, in his opinion, the cynical and extortionary monopoly of Western Union. The Hubbard bill did not offer to completely nationalize the existing telegraph companies, as almost all European powers did, but would establish a government-sponsored telegraph service under the auspices of the postal ministry. But the result would, most likely, be the same, and Western Union would leave this business. By the mid-1870s, the advancement of the law had stalled, but Hubbard was confident that control of a critical new telegraph patent could give him an advantage to push his proposal in Congress.


Gardiner Green Hubbard

In the United States there are two unique factors: first, the continental scale of Western Union. None of the European telegraph organizations had such long lines, and, consequently, there were no reasons for the development of multiplexed telegraphy. Secondly, the open question of government control over the telegraph. The last European stronghold was Britain, which nationalized the telegraph in 1870. After that, nowhere except the US, there were no places left where the tempting prospect of making a technological breakthrough and undermining the monopoly would loom. Perhaps because of this, most of the work on the harmonic telegraph was done in the USA.

The prize claimed mostly three. Two of them were already venerable inventors - Elisha Gray and Thomas Edison.. The third was a professor of rhetoric and a teacher for the deaf by the name of Bell.

Gray

Elisha Gray grew up on a farm in Ohio. Like many of his contemporaries, in his adolescence, he played with telegraphy, but at 12, when his father died, he began to look for an occupation that could provide him. For some time he was a student of a blacksmith, then a ship's carpenter, and at 22 he learned that he could get an education at Oberlin College, without stopping the carpenter. After five years of study, he plunged into the career of an inventor in the field of telegraphy. His first patent was a self-adjusting relay, which, using the second electromagnet instead of the spring returning the armature, eliminated the need to adjust the sensitivity of the relay depending on the current in the circuit.


Elisha Gray, approx. 1878

By 1870, he was already a partner in a company producing electrical equipment, and worked there as a chief engineer. In 1872, he and his partner moved the company to Chicago and renamed it the Western Electric Manufacturing Company. Soon, Western Electric became the main supplier of telegraph equipment for Western Union. As a result, it will leave a noticeable mark in the history of telephony.

In early 1874, Gray heard a strange sound from his bathroom. It sounded like a howl of a vibrating rheotome, only much stronger. Rheotome (literally “flow breaker”) was a well-known electrical device that used a metal tongue to quickly open and close the loop. Looking into the bathroom, Gray saw his son holding an induction coil connected to the rototomy in one hand, and rubbing the zinc bath with his second hand, which was buzzing with the same frequency. Gray, interested in the opportunities that had opened up, walked away from the daily work at Western Electric to re-invent. By the summer, he had developed a full-music musical telegraph, with which it was possible to play sounds on a diaphragm made of a metal pelvis, by pressing the keys of the keyboard.


Transmitter


Receiver The

Musical Telegraph was a novelty with no obvious commercial value. But Gray realized that the possibility of transmitting sounds of different pitch via one wire gave him two possibilities. With a transmitter of another design, capable of capturing sound from the air, it was possible to create a voice telegraph. With another receiver capable of dividing the combined signal into components, it was possible to make a harmonic telegraph - that is, a multiplex telegraph based on sound. He decided to concentrate on the second option, since the telegraph industry had obvious requests. He confirmed his choice after learning of Reis' phone, which seemed to be a simple philosophical toy.

The receiver of the harmonic telegraph Gray was made from a set of electromagnets coupled with metal strips. Each strip was tuned to a specific frequency, and sounded when the corresponding button was pressed on the transmitter. The transmitter worked on the same principle as the music telegraph.

Gray improved his apparatus for the next two years and took him to the exhibition. Officially, the event was called "The International Exhibition of Arts, Industrial Products and Products of Soils and Mines"It was the first international exhibition held in the United States, and it coincided with the celebration of the centenary of the nation, in connection with which it presented the so-called" Hundred Years Exposition ". It passed in Philadelphia in the summer of 1876. There Gray demonstrated the" octruple "The connection (that is, the transmission of eight messages simultaneously) on a specially prepared telegraph line from New York. This achievement was highly appreciated by the judges of the exhibition, but soon it was eclipsed by an even greater miracle.

Edison

William Orton , president of Western Union, quickly found out about Gray's progress, which made him very nervous. At best, with Gray's success, the situation will turn into a very expensive patent licensing. In the worst case, Gray's patent will be the basis for creating a competing company that will shatter the dominance of Western Union.

Therefore, in July 1875, Orton pulled an ace from his sleeve, namely Thomas Edison. Edison grew side by side with telegraphy, spent several years as a telegraph operator, and then became an inventor. His highest triumph at that time was a quadruplex relationship created with the money of Western Union a year earlier. Now Orton was hoping that he would improve his invention and surpass what Gray had managed to do. He provided Edison with a description of Reis' phone; Edison also studied the work of Helmholtz, recently translated into English.



Edison was at the peak of form, and innovative ideas poured out of him like sparks from the anvil. In the following year, he showed two different approaches to the acoustic telegraph - the first was similar to Gray's telegraph, and used tuning forks or vibrating tongues to create or perceive the desired frequency. Edison failed to make such a device work at an acceptable level.

The second approach, which he called the "acoustic transmitter", was completely different. Instead of using vibrating reeds to transmit different frequencies, he used them to transmit pulses at different intervals. He divided the use of the wire between transmitters by time, not frequency. This required perfect synchronization of vibrations in each pair of receiver-transmitter, so that the signals do not overlap. By August 1876, a quadruplex worked on this principle for him, although at a distance of more than 100 miles the signal became useless. He also had ideas about improving Reis' phone, which he temporarily set aside.

And then Edison heard about the sensation produced at the Centennial Exposition in Philadelphia by a man named Bell.

Bell

Alexander Graham Bell was born in Edinburgh, Scotland, and grew up in London under the sensitive guidance of his grandfather. Like Gray and Edison, in his adolescence he showed interest in the telegraph, but then he followed in the footsteps of his father and grandfather, choosing human speech as his main passion. His grandfather, Alexander, made a name for himself on stage, and then began to teach oratory. His father, Alexander Melville, was also a teacher, and even developed and published a phonetic system, which he called “visible speech”. The younger Alexander (Alec, as he was called in the family), chose to teach deaf speeches as his occupation.

By the end of the 1860s, he was engaged in anatomy and physiology at University College London. Together with him studied student Marie Eccleston, whom he was going to marry. But then he refused to learn, and from love. His two brothers died of tuberculosis, and Alec’s father demanded that he and the rest of his family emigrate to the New World in order to preserve his only son’s health. Bell complied, although he resisted and resented about this, and set sail in 1870.

After a little hack in Ontario, Alexander, not without his father’s connections, found a job as a teacher at a deaf school in Boston. There the threads of his future began to stumble.

First, he had a student, Mabel Hubbard, who lost her hearing at the age of five due to scarlet fever. Bell did private tutoring even after becoming a professor of vocal physiology and oratory at Boston University, and Mabel was among his first students. During her studies, she was a little less than 16 years old, ten years less than Bella, and in a few months he fell in love with this girl. We will return to her story.

In 1872, Bell renewed his interest in telegraphy. A few years before, while still in London, Bell had learned about the Helmholtz experiments. But Bell misunderstood the achievement of Helmholtz, believing that he not only created, but also transmitted complex sounds with the help of electricity. So Bell got carried away by the harmonic telegraph - sharing the wire with several signals transmitted at several frequencies. Perhaps inspired by the news that Western Union acquired the idea of ​​a duplex telegraph from Joseph Sturns, his fellow countryman from Boston, Bell reviewed his ideas and, like Edison and Gray, began to try to implement them.

One day while visiting Mabel, he touched the second thread of his destiny - standing next to the piano, he showed her family a trick he had learned in his youth. If you sing a clean note on the piano, the corresponding string will tingle and play it back to you. He told Mabel's father that a tuned telegraph signal could achieve the same effect, and explained how this can be used in multiplexed telegraphy. And Bell would not have found a listener better tuned to his story: he resonated with joy and instantly understood the main idea: “there is only one air for everyone, and only one wire is needed”, that is, the wave propagation of current in the wire can copy the distribution in miniature air waves generated by complex sound. Bella's listener was Gardiner Hubbard.

Phone

And now the story becomes very confusing, so I’m afraid to try out the patience of the readers. I will try to track the main trends, not getting stuck in the details.

Bell, supported by Hubbard and the father of another of his students, worked diligently on the harmonic telegraph, without disclosing his successes. He alternated fierce work with periods of rest when his health failed, while trying to fulfill his university duties, promote his father's "visible speech" system and work as a tutor. He hired a new assistant, Thomas Watson, an experienced mechanic from the Charles Williams Boston machine shop - people interested in electricity gathered there. Hubbard urged Bell, and did not hesitate to even use his daughter’s hand as an incentive, refusing to marry her until Bell improved his telegraph.

In the summer of 1874, during a vacation near the family home in Ontario, Bella condescended to enlightenment. Several thoughts that existed in his subconscious, merged into one - the phone. His thoughts were influenced not least by the phonoautograph- the world's first recording device, drawing sound waves on smoked glass. This convinced Bell that the sound of any complexity can be reduced to a point in space, such as the movement of a current through a wire. We will not dwell on the technical details, because they have no relation to the really created phones and the practicality of their use is questionable. But they sent Bell’s thinking in a new direction.


A sketch of the concept of the initial version of Bell’s telephone with “harmonics” (was not built)

Bell temporarily postponed this idea so that, as his partners expected, to pursue the goal of creating a harmonic telegraph.

But the routine of fine-tuning the tools was soon tired of him, and his heart, tired of many practical obstacles standing in the way of a working prototype to a practical system, became increasingly tangible towards the telephone. The human voice was his first passion. In the summer of 1875, he discovered that vibrating tongues could not only quickly close and open the circuit in the manner of a telegraph key, but also create a continuous wave-like current, moving in a magnetic field. He told his phone idea to Watson, and together they built the first phone model on this principle - the diaphragm vibrating in the electromagnet field excited a wave-like current in the circuit of the magnet. This device was able to transmit some muffled voice sounds. Hubbard was not impressed with the device and ordered Bell to return to real problems.


Bell's rudimentary telephone "gallows" of the summer of 1875

But Bell still convinced Hubbard and the other partners that the idea should be patented, since it could be used in multiplexed telegraphy. And if we apply for a patent, no one will forbid to mention in it the possibility of using the device for voice communications. Then in January, Bell added a new wave current generation mechanism to the patent draft: variable resistance. He wanted to connect the vibrating diaphragm, which received the sound, with a platinum contact, falling and rising from the tank with acid, in which there was another, fixed contact. When the moving contact plunged deeper, the surface of a larger area contacted the acid, which reduced the resistance to the current flowing between the contacts - and vice versa.


Bell's concept of a fluid variable-resistance transmitter concept

Hubbard, knowing that Gray is approaching Bella on the heels, sent a patent current wave application to the patent office on the morning of February 14th, without waiting for the final confirmation from Bell. And the same day, Gray's lawyer arrived with his patent. It also contained a proposal for the generation of the wave current using liquid AC resistance. It also mentioned the possibility of using the invention for both the telegraph and voice transmission. But he was a few hours late to interfere with Bell's patent. If the order of arrival was different, then before issuing permission for a patent, it would be necessary to conduct long hearings on priorities. As a result, on March 7, Bell was granted a patent number 174,465, "Improvements in telegraphy", which laid the cornerstone for the future dominance of the Bell system.

But this dramatic story has not been without irony. For on February 14, 1876, neither Bell nor Gray built a working phone model. No one even tried to do this, except for Bell’s short attempt last July, in which there was no alternating resistance. Therefore, you should not consider patents as milestones in the history of technology. This critical moment in the development of telephony as a business enterprise was practically not connected with the telephone as a device.

Only after sending the patent did Bell and Watson have the opportunity to return to the telephone, despite Hubbard's constant demands to continue work on the multiplexed telegraph. Bell and Watson tried for several months to get the idea to work with liquid variable resistance, and the phone built on this principle was used to convey the famous phrase: "Mr. Watson, come here, I want to see you."

But inventors constantly had problems with the reliability of these transmitters. Therefore, Bell and Watson began working on new transmitters, using the principle of magneto, with which they experimented in the summer of 1875 - using the movement of the diaphragm in a magnetic field to directly excite the current. The advantage was simplicity and reliability. The disadvantage was that the low power of the telephone signal was due to the vibrations of the air generated by the speaker’s voice. This limited the effective working distance of the transmitter-magneto. And for a device with variable resistance, the voice modulated the current generated by the battery, which could be made arbitrarily strong.

The new magneto worked much better than those that were last summer, and Gardiner decided that there could be something in the idea of ​​the phone. Among other entertainment, he participated in the committee of education and scientific exhibitions of Massachusetts in the approaching Hundred Years exposition. He used his influence to give Bell a place in an exhibition and competition where judges judged electrical inventions.


Magneto Bell / Watson Transmitter. The vibrating metal diaphragm D moves in the magnetic field of the magnet H and excites a current in the circuit.


Receiver

The judges arrived to Bell immediately after studying Gray's harmonic telegraph. He left them at the receiver and went to one of the transmitters located a hundred meters further along the gallery. The interlocutors of Bell were amazed to hear his singing and the words coming out of a small metal box. One of the judges was Bella's fellow countryman, Scot William Thomson (who was later granted the title Lord Kelvin). He excitedly ran to the other end of the hall to Bell, to inform him that he had heard his words, and later declared the phone "the most amazing thing he had seen in America." There was also the Brazilian emperor, who first pressed the box to his ear, and then jumped up from his chair, shouting: “I hear, I hear!”

The hype caused by Bell at the show forced Edison to take up her previous ideas of a telephone transmission. He immediately pounced on the main drawback of the Bell device - the frail transmitter-magneto. From his experiments with quadruplex, he knew that the resistance of coal chips varied with pressure. After many experiments with different configurations, he developed a variable resistance transmitter operating on this principle. Instead of a pressure wave of the speaker talking in contact with the fluid, the carbon “button” was compressed, its resistance was changed, and, consequently, the current strength in the circuit was changed. It was much more reliable and easier to implement than the fluid transmitters conceived by Bell and Gray, and was a decisive contribution to the long-term success of the phone.



Still, Bell was the first to make the phone, despite the obvious advantages in the experience and skills that his rivals had. He was the first not because he was visited by an insight that others did not reach - they also thought of the phone, but they found it insignificant compared to the improved telegraph. Bell was the first because he liked the human voice more than the telegraph, he liked it so much that he resisted the wishes of his partners until he was able to prove the efficiency of his phone.

And what about the harmonic telegraph on which Gray, Edison and Bell spent so much effort and thought? Nothing happened yet. Keeping the mechanical vibrators at both ends of the wire perfectly tuned turned out to be very difficult, and no one knew how to amplify the combined signal so that it worked at long distances. Only closer to the middle of the 20th century, after the electrical technologies that began with the radio allowed to create fine tuning of frequencies and low-noise amplification, did the idea of ​​superimposing multiple signals for transmission over a single wire turned into reality.

Farewell to Bell

Despite the success of the phone at the exhibition, Hubbard was not interested in building a telephone system. The following winter, he suggested to William Orton, President of Western Union, to acquire all the rights to the telephone according to Bell's patent for $ 100,000. Orton refused, under the influence of a combination of dislike for Hubbard and his schemes with the postal telegraph, Edison’s confidence in his work and his phone, and also the belief that telephone compared to telegraph meant very little. Other attempts to sell the idea of ​​the phone were not crowned with success, mainly due to fears of the huge costs of litigation over patent rights in the event of commercialization. Therefore, in July 1877, Bell and his partners founded the Bell Telephone Company to organize the telephone service themselves. That same month, Bell finally married Mabel Gardiner at her family’s home,


Alec with his wife Mabel and two surviving children - his two sons died in infancy (c. 1885)

The following year, Orton changed his attitude to the telephone and set up his company, the American Speaking Telephone Company, hoping that Edison, Gray and others' patents would protect the company from Bell’s legal attacks. She became a deadly threat to Bell's interests. Western Union had two major advantages. First, large financial assets. Bella needed money because it was renting out the equipment to its customers, which required many months to pay back. Secondly, access to an improved Edison transmitter. Anyone who compared his transmitter with a Bell device could not help but note the better clarity and loudness of the voice of the first. Bell's company had no choice but to file a competitor in court, filing a patent infringement lawsuit.

If Western Union had unequivocal rights to the only affordable high-quality transmitter, it would have a powerful lever to reach an agreement. But Bella’s team unearthed a previous patent for a similar device obtained by the German émigré Emil Berliner and bought it back. Only after many years of legal battles, the Edison patent was given priority. Seeing that the trial was not successful, in November 1879, Western Union agreed to transfer all patent rights to the telephone, equipment and existing subscribers (55,000 people) to Bell’s company. In exchange, they asked only 20% of the phone rental for the next 17 years, and also that Bell did not climb into the telegraph business.

Bell's company quickly replaced Bell's devices with improved models based first on the Berliner patent, and then on patents obtained from Western Union. By the time the litigation ended, Bell's main occupation was testifying on patent litigation, of which there were plenty. By 1881, he completely retired. Like Morse, and unlike Edison, he was not the creator of systems. Theodore Vale, an energetic manager whom Gardiner lured from the postal service, took the company into his own hands and led her to a dominant position in the country.

Initially, the telephone network grew quite differently from the telegraph. The latter developed leaps from one commercial center to another, overcoming 150 km at a time, looking for points of the highest concentration of valuable customers, and only then supplementing the network with links to smaller local markets. Telephone networks grew like crystals from small points of growth, from several customers located in independent clusters in each city and surrounding area, and slowly, over the decades, merged into regional and national structures.

There were two obstacles to large-scale telephony. First, there was the problem of distance. Even with amplifiers of variable resistance, created on the basis of Edison's idea, the range of telegraph and telephone work was incomparable. The more complex signal of the telephone was more susceptible to noise, and the electrical properties of fluctuating currents were known worse than the properties of the direct current used in the telegraph.

Secondly, there was a communication problem. Bell's telephone was a one-on-one communication device; he could connect two points over a single wire. For the telegraph this was not a problem. One office could serve a multitude of customers, and messages could be easily redirected from the central office via another line. But there was no easy way to transfer a telephone conversation. In the first implementation of the phone, the third and subsequent people could connect with two people who spoke only through what they would later call “paired phone”. That is, if all subscriber devices were attached to the same line, then each of them could talk (or eavesdrop) with the others.

We will return to the problem of distance in due time. In the next part we delve into the problem of connections and its consequences, which had an impact on the development of the relay.

What to read

• Robert V. Bruce, Bell: Alexander the Graham Bell and the Conquest of Solitude (1973)
• David A. Hounshell, “Elisha Gray and the Telephone: On the Disadvantages of Being an Expert”, Technology and Culture (1975).
• Paul Israel, Edison: A Life of Invention (1998)
• George B. Prescott, The Speaking Telephone, Talking Phonograph, and Other Novelties (1878)