Relay history: electronic era

In the previous series:

• The forgotten generation of relay computers [ translation]
Relay history: just connect


Last time we saw how the first generation of digital computers was built on the basis of the first generation of automatic electrical switches - electromagnetic relays. But by the time these computers were created, behind the scenes another digital switch was waiting for its release. The relay was an electromagnetic device (using electricity to control a mechanical switch), and a new class of digital switches was electronic — based on new knowledge about an electron that appeared at the beginning of the 20th century. This science indicated that the carrier of the electric force was not current, not wave, not field, but a solid particle.

The device that spawned the era of electronics, based on this new physics, became known as the "vacuum tube" [in the United States - vacuum tube, or "vacuum tube"]. Two people are involved in the history of its creation: the Englishman Ambrose Fleming and the American Lee de Forest . In fact, the origin of electronics is more complex, it is twisted from a multitude of threads crossing Europe and the Atlantic, and stretching back into the past, right up to early experiments with Leiden banks in the middle of the 18th century.

But as part of our presentation, it will be convenient to cover (pun intended) this story, starting with Thomas Edison. In the 1880s, Edison made an interesting discovery while working on electric lighting - this discovery sets the stage for our story. This led to the further development of electronic lamps, which was required for two technological systems: a new form of wireless messaging and ever-expanding telephone networks.

Prologue: Edison

Edison is usually considered the inventor of the light bulb. This at the same time does him too much and too little honor. Too much, since not one Edison came up with a glowing lamp. In addition to the crowd of inventors who preceded him, whose creations did not reach commercial applications, we can mention Joseph Swan and Charles Stirn from Britain and American William Sawyer, who brought light bulbs to the market simultaneously with Edison. [The honor of the invention also belongs to the Russian inventor Lodygin Alexander Nikolaevich . Lodygin was the first who thought to pump air out of a glass tube bulb, and then suggested to make a glowing wire not from coal or charred fibers, but from refractory tungsten / approx. trans. ]. All lamps consisted of a sealed glass bulb, inside which resistive filament was located. When the lamp was turned on in the circuit, the heat generated by the resistance of the thread to the current made it glow. Air was pumped out of the flask so that the thread would not catch fire. Electric light was already known in large cities as arc lamps used to illuminate large public spaces. All these inventors were looking for a way to reduce the amount of light, taking a bright piece of a burning arc, small enough to use it in homes to replace gas lamps, and make the light source safer, cleaner and brighter.

And what Edison really did — or rather, created his industrial laboratory — is not just the creation of a light source. They built a whole electrical system for lighting homes — generators, current wires, transformers, and so on. Of all this, the bulb was only the most obvious and visible component. The presence of Edison’s name in his electricity generating companies was not a simple kneeling in front of a great inventor, as is the case with Bell Telephone. Edison proved to be not only an inventor, but also a system architect. His laboratory continued to work on improving the various components of electric lighting, even after their early success.

Copy of early edison lamps

During the research somewhere in 1883, Edison (and possibly one of his employees) decided to enclose a metal plate inside the luminous lamp along with the thread. The reasons for this act are unclear. Perhaps it was an attempt to eliminate the darkening of the lamp - the inside of the glass bulb eventually accumulated a mysterious dark substance. The engineer apparently hoped that these black particles would be attracted to the live plate. To his surprise, he discovered that when the plate was included in the circuit along with the positive end of the thread, the current flowing through the thread was directly proportional to the intensity of the glow of the thread. When the plate was connected to the negative end of the filament, nothing like this was observed.

Edison decided that this effect, later called the Edison effect or thermionic emission , can be used to measure or even control the “electromotive force” or voltage in an electrical system. By virtue of habit, he filed a patent application for this "electric indicator", and then returned to more important tasks.

Without wires

Fast forward to 20 years in the future, in 1904 minutes. At this time in England, John Ambrose Fleming worked on the instructions of the Marconi Company to improve the radio wave receiver.

It is important to understand what was and what was not the radio at that time, both in terms of the instrument and in terms of practice. Radio was not even called “radio” at that time, it was called “wireless”, wireless. The term "radio" began to prevail only in the 1910s. Specifically, it meant a wireless telegraph - a system for transmitting signals in the form of points and a dash from the sender to the receiver. Its main use was the connection between ships and port services, and in this sense they were interested in the marine departments of the whole world.

Some inventors of the time, in particular Reginald Fessenden , experimented with the idea of ​​a radiotelephone - transmitting voice messages over the air in the form of a continuous wave. But the broadcast in the modern sense arose only 15 years later: the transfer of news, stories, music and other programs to receive a wide audience. Prior to this, the omnidirectional nature of radio signals was viewed as a problem to be solved, and not as a feature that could be used.

The radio equipment that existed at that time was well adapted for working with Morse code and bad for everything else. Transmitters created Hertz's waves, sending a spark through a gap in the circuit. Therefore, the signal was accompanied by a crash of statics.

The receivers recognized this signal through a coherer: metal filings in a glass tube, knocked under the influence of radio waves into a continuous mass, and thus closed the circuit. Then it was necessary to knock on the glass so that the sawdust would disintegrate and the receiver would be ready for the next signal — at first it was done manually, but soon automatic devices appeared for that.

In 1905, crystal detectors , also known as catlike whiskers, began to appear. It turned out that just touching the wire of a certain crystal, for example, silicon, iron pyrites or galena , one could snatch a radio signal from the air. The resulting receivers were cheap, compact and accessible to everyone. They stimulated the development of amateur radio, especially among young people. The sudden surge in the employment of airwaves, which arose as a result of this, led to problems due to the fact that the radio broadcast was shared among all users. The lovers' innocent conversations could accidentally cross with the talks of the morflot, and some hooligans even managed to give false orders and send signals for help. The state inevitably had to intervene. As Ambrose Fleming himself wrote, the appearance of crystal detectors
Immediately led to a surge of irresponsible radio telegraphy due to the tricks of an innumerable number of amateur electricians and students, which required the harsh intervention of national and international authorities to keep what was happening within a reasonable and safe.

Of the unusual electrical properties of these crystals, the third generation of digital switches will appear in its time, followed by relays and lamps — the switches that dominate our world. But everything has its time. We have described the scene, now we will return all attention to the actor who has just appeared in the spotlight of the spotlights: Ambrose Fleming, England, 1904.


In 1904, Fleming was a professor of electrical engineering at University College London, and a consultant for the Marconi Company. Initially, the company hired him to obtain an expert assessment for the construction of a power plant, but then he took up the task of improving the receiver.

Fleming in 1890

Everyone knew that the coherer was a poor receiver in terms of sensitivity, and the magnetic detector developed at Macroni was not particularly better. To find a replacement for him, Fleming first decided to build a sensitive circuit to detect Hertz waves. Such a device, even without becoming a detector in itself, would be useful in future studies.

To do this, he needed to think of a way to constantly measure the strength of the current generated by the incoming waves, instead of using a discrete coherer (he showed only the states on - where the sawdust stuck together, or off). But the known devices for measuring current strength - galvanometers - required a constant, that is, unidirectional current to operate. The alternating current, excited by radio waves, changed direction so quickly that no measurement would have worked.

Fleming remembered that several interesting things were gathering dust in his closet — Edison indicator lights. In the 1880s, he was a consultant for the Edison Electric Lighting Company in London, and worked on the problem of blackening lamps. At that time, he received several copies of the indicator, perhaps from William Price, the chief electrical engineer of the British Postal Service, who had just returned from an electric exhibition in Philadelphia. At that time, outside the United States, postal control over telegraph and telephone was common, so they were centers of electrical expertise.

Later, in the 1890s, Fleming himself studied the Edison effect using lamps obtained from Pris. He showed that the effect was that the current flowed in one direction: a negative electric potential could flow from the hot filament to the cold electrode, but not vice versa. But only in 1904, when he faced the task of detecting radio waves, he realized that this fact can be used in practice. The Edison indicator will allow only one-way AC pulses to bridge the gap between the thread and the plate, which will give a constant and unidirectional flow.

Fleming took one lamp, connected it in series with a galvanometer, and turned on the spark transmitter. Voila - the mirror turned, and the beam of light shifted on the scale. It worked. He could accurately measure the incoming radio signal.

Fleming valve prototypes. The anode is in the middle of the thread loop (hot cathode)

Fleming called his invention "valve" because it only let electricity pass in one direction. Speaking in more general electrical language, it was a rectifier - a way to convert AC to DC. Then it was called a diode, because it had two electrodes — a hot cathode (thread) that emitted electricity, and a cold anode (plate) that received it. Fleming introduced several improvements to the design, but in essence the device was no different from an indicator lamp made by Edison. Its transition to a new quality occurred as a result of a change in the way of thinking - this phenomenon we have already seen many times. The change occurred in the world of ideas in Fleming's head, and not in the world of things outside of it.

The valve of Fleming itself was helpful. It was the best field device for measuring radio signals, and a good detector in itself. But he did not shake the world. The explosive growth of electronics began only after Lee de Forest added a third electrode and turned the valve into a relay.


Lee de Forest had an unusual upbringing for a Yale student. His father, Rev. Henry de Forest, was a civil war veteran from New York, pastor of the congregational church , and firmly believed that as a preacher should spread the divine light of knowledge and justice. In obedience to the call of duty, he accepted the invitation to become president of Talladeg College in Alabama. The college was founded after the Civil War by the American Missionary Association, based in New York. It was intended to train and instruct local black people. There, Lee felt himself between a hammer and an anvil - local negros humiliated him for his naivety and cowardice, and local whites for his being a Yankee .

And yet, the young men de Forrest developed a strong self-confidence. He discovered in himself a penchant for mechanics and inventions - his large-scale model of a locomotive became a local miracle. Even as a teenager, while studying at Talladeg, he decided to devote his life to inventions. Then, being a young man and living in the city of New Haven, the pastor’s son threw off his last religious beliefs. They gradually left due to acquaintance with Darwinism, and then they blew away like the wind after the untimely death of his father. But the feeling of having a destination did not leave de Forrest - he considered himself a genius and sought to become the second Nikola Tesla, the rich, famous and mysterious wizard of the electricity era. His classmates from Yale University considered him a complacent windbag. Perhaps he can be called the least popular person among all those encountered in our history.

de Forest, ca.1900

After graduating from Yale University in 1899, de Forest chose the development of the art of transmitting wireless signals that was gaining momentum as a path to wealth and fame. In the following decades, he stormed this path with great determination and confidence, and without any hesitation. It all started with the joint work of de Forest and his partner Ed Smythe in Chicago. Smythe kept their company afloat with regular payments, and together they developed their own radio wave detector, consisting of two metal plates connected by glue, which de Forest called “paste” [goo]. But de Forest could not wait long awards for his genius. He got rid of Smythe and cooperated with a dubious New York-based financier named Abraham White [ who ironically changed his name from the one given to him at birth, Schwartz, to hide his dark deeds. White / White - (eng.) White, Schwartz / Schwarz - (German) black / approx. trans. ] by opening the De Forest Wireless Telegraph Company.

The very activity of the company was secondary for both our heroes. White used the ignorance of people to fill their pockets. He lured millions from investors, struggling to keep up with the expected radio boom. And de Forest, thanks to the abundant flow of funds of these “suckers”, has concentrated on proving his genius through the development of a new American system of wireless transmission of information (in contrast to the European one, developed by Marconi and others).

Unfortunately for the American system, the detector de Forrest did not work particularly well. For a while, he solved this problem by borrowing Reginald Fessenden's patented design for a detector called “liquid barette” - two platinum wires immersed in a bath of sulfuric acid. Fessenden filed a lawsuit because of patent infringement - and he would obviously have won this lawsuit. De Forest could not calm down until he would come up with a new detector that belonged only to him. In the autumn of 1906, he announced the creation of such a detector. At two different meetings at the American Institute of Electrical Engineering, de Forest described his new wireless detector, which he called "Audion". But its real origin is in doubt.

For some time, De Forest's attempts to build a new detector revolved around the passage of current through the Bunsen burner flame, which, in his opinion, could be an asymmetric conductor. The idea, apparently, was not crowned with success. At some point in 1905, he learned about the valve of Fleming. De Forest hammered that this valve and its device based on the burner were basically no different - if you replace the hot thread with a flame and cover it with a glass bulb to limit the gas, you will get the same valve. He developed a series of patents that repeated the history of inventions that preceded the Fleming valve with gas flame-based detectors. He obviously wanted to give himself priority in the invention, bypassing the Fleming patent, since the work with the Bunsen burner preceded the work of Fleming (they had been running since 1900).

It is impossible to say whether it was self-deception or fraud, but the result was De Forest's patent of August 1906 for "a devastated glass vessel containing two separate electrodes, between which there is a gaseous medium, which, with sufficient heating, becomes a conductor and forms a sensitive element." The equipment and the operation of the device belong to Fleming, and the explanation of his work is to de Forest. De Forest, as a result, lost the patent dispute, although it took ten years.

The impatient reader may already begin to wonder why we are spending so much time on this person, whose self-proclaimed genius was in giving out other people's ideas for his own? The reason lies in the transformations that Audion underwent in the last few months of 1906.

By then, de Forest was out of work. White and his partners escaped responsibility for the Fessenden lawsuit by creating a new company, United Wireless, and lending American De Forest assets for $ 1. De Foresta was expelled with $ 1,000 compensation and several useless patents on his hands, including the Audion patent. Accustomed to a wasteful lifestyle, he faced serious financial difficulties and desperately tried to turn the Audion into a great success.

In order to understand what happened next, it is important to know that de Forest believed that he invented the relay - in contrast with the Fleming rectifier. He made his Audio by connecting the battery to the cold plate of the valve, and believed that the signal in the antenna circuit (connected to the hot thread) modulated a more powerful current in the battery circuit. He was wrong: it was not two schemes, the battery simply shifted the signal from the antenna, and did not amplify it.

But this error became critical, since it led de Forest to experiment with the third electrode in the flask, which should have further separated the two circuits of this “relay”. At first he added the second cold electrode next to the first one, but then, perhaps under the influence of the control mechanisms used by physicists to redirect the rays in the electron-beam devices, he moved the electrode to the space between the filament and the primary plate. He decided that such a situation could interrupt the flow of electricity, and changed the shape of the third electrode from the plate to a wavy wire, resembling a rasp - and called it "grid".

Triode Audion 1908. The thread (torn) on the left is the cathode, the wavy wire is the grid, the rounded metal plate is the anode. He still has a thread like an ordinary light bulb.

And it really was a relay. A weak current (such as that obtained from a radio antenna) applied to the grid could control a much stronger current between the filament and the plate, pushing off charged particles trying to cross between them. This detector worked much better than the valve, since it not only straightened out, but also amplified the radio signal. And, like the valve (and in contrast to the coherer), it could issue a constant signal, which made it possible to create not only wireless, but also a radio telephone (and later - voice and music transmission).

In practice, he did not work very well. The de Foresta audions were fastidious, they quickly burned, there was a lack of consistent quality in their production, and they were ineffective as amplifiers. In order for a particular Audion to work properly, it was necessary to adjust the electrical parameters of the circuit for it.

However, de Forest believed in his invention. For his advertising, he organized a new company, De Forest Radio Telephone Company, but sales were scanty. The biggest success was the sale of equipment to the fleet for intra-fleet telephony during the circumnavigation of the Great White Fleet . However, the fleet commander, having no time to force de Forest’s transmitters and receivers to work and train the team to use them, ordered them to be packaged and left in storage. Moreover, de Forest's new company, led by a follower of Abraham White, was no more decent than the previous one. In addition to his setbacks, he soon came under fraud charges.

For five years, Audion has achieved nothing. And again, the phone will play a key role in developing a digital relay, this time saving a promising, but untested technology that was on the verge of oblivion.

And again the phone

The long-distance communications network was AT & T’s central nervous system. She tied together many local companies and provided a key competitive advantage after the expiration of Bell's patents. By joining the AT & T network, a new customer could, in theory, get through to all the other subscribers that were thousands of kilometers away from him — although in reality long distance calls were rarely made. Also, the network was the material basis for the comprehensive ideology of the One Policy, One System, Universal Service company.

But with the beginning of the second decade of the twentieth century, this network reached the physical maximum. The further the telephone wires went, the weaker and noisier the signal passing through them became, and as a result the speech became almost indistinguishable. Because of this, in the US there were actually two AT & T networks separated by a continental ridge.

For the eastern network, the peg was New York, and mechanical repeaters and Pupin's coils were the tie that determined how far a human voice could reach. But these technologies were not omnipotent. Coils changed the electrical properties of the telephone circuit, reducing the attenuation of voice frequencies - but they could only reduce it, not eliminate it. ( , ) . 1911 - . , , . 1909 , AT&T, . – - - 1915-.

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