Relay history: just connect

The first phones worked one on one, connecting one pair of stations. But already in 1877, Alexander Graham Bell imagined a universal coherent system. Bell wrote in a promotional paper for potential investors that, just as municipal gas and water networks connect homes and offices in large cities with distribution centers,

You can imagine how the cables of telephone wires will be laid underground or suspended at the top, and their branches will pass into private houses, country estates, shops, factories, etc., etc., combining them with the help of a main cable with central office, where the wires can be connected as you like, establishing a direct connection between any two places in the city. Moreover, I believe that in the future the wires will connect the head offices of the Telephone Company in different cities, and a person from one part of the country will be able to communicate with another person from a remote place.

But neither he nor his contemporaries had a technical opportunity to implement these forecasts. For decades and the use of a large proportion of ingenious inventions and hard work will be needed to turn the phone into the most extensive and sophisticated machine known to humanity that crosses the continents, and as a result, the oceans to connect any telephone station in the world with any other.

This transformation was made possible thanks to, among other things, the development of a switchboard - a central office with equipment capable of redirecting the call from the line of the caller to the line of the called. Automation of switches has led to a significant increase in the complexity of relay circuits, which greatly influenced computers.

First switches

In the early days of the phones, no one could say for sure why they were needed. The transmission of recorded messages over long distances has already been mastered and has shown its advantage in commercial and military applications. But there was no precedent for the transmission of sound over long distances. Was it a telegraph type business instrument? Social communication device? Means for entertainment and moralizing, like music broadcasts and political speeches?

Gardiner Green Hubbard, one of Bell's main sponsors, found one useful analogy. Over the past decades, telegraph entrepreneurs have built many local telegraph companies. Wealthy people or small businesses rented a dedicated telegraph line connecting them to the company's central office. Having sent a telegram, they could call a taxi, send a courier with a message to a client or friend, call the police. Hubbard believed that in such matters the telephone could replace the telegraph. It is much easier to use, and the ability to maintain voice contact accelerates the service and reduces misunderstanding. Therefore, he encouraged the creation of just such a company that offered to rent telephones associated with local telephone companies, both recently formed and converted from telegraph stations.

The manager of one of these phone companies might have noticed that he needed twenty phones to talk to twenty clients. And in some cases, one client wanted to send a message to another - for example, a doctor sending a prescription to a pharmacist. Why not just give them the opportunity to communicate with each other?

Bell himself could also give such an idea. He spent most of the year 1877 on tours with lectures promoting the telephone. George Coy listened to one of these lectures in New Haven, Connecticut, when Bell ranted about his vision for the central telephone office. Coy was inspired by the idea, organized the New Haven District Telephone Company, acquired a license from Bell Company and found the first subscribers. By January 1878, he had connected 21 subscribers with the help of the first public telephone switchboard, making it from used wires and pens from teapot covers.


During the year, the same handicraft devices for local telephone subscribers began to appear throughout the country. The speculative public telephone use model began to crystallize around these local communication sites - between vendors and suppliers, businessmen and customers, doctors and pharmacists. Even between friends and buddies who were rich enough to afford such luxury. Alternative methods of using the phone (for example, as a means for broadcasting) began to gradually disappear.

For several years, telephone offices have come together on the general scheme of equipment for switches, which will consistently exist for many decades: an array of sockets that the operator could connect using connected wires. They agreed on the ideal field for the operator. At first, telephone companies, many of which grew out of telegraphic offices, hired people from the available labor force — young clerks and messengers. But customers complained about their rudeness, and managers suffered from their violent behavior. Pretty soon they were replaced by polite, decent girls.

The further development of these central switches will determine the competition for dominance in the field of telephony between the Bell company, serving in the Goliath class, and the emerging independent competitors.

Bell and independent companies

The American Bell Telephone Company, owning Bell’s patent of 1876 for number 174,465 for “telegraph improvements”, was in an extremely advantageous position due to the rather wide area covered by the patent. The court ruled that this patent included not only certain tools described in it, but also the principle of transmitting sound through the wave current, resulting in giving Bell a monopoly on telephony in the United States until 1893, when the 17-year patent expired.

Management companies wisely used this term. Especially worth noting are President William Forbes and Theodore Weil . Forbes was a Boston aristocrat and the main one from the list of investors who took control of the company when Bell's early partners ran out of money. Weil, the grand-nephew of Samuel Morse's partner Alfred Weil , was the president of the most important of the Bell companies, the Metropolitan Telephone, located in New York, and was the general manager of American Bell. Weil showed his managerial character as the head of the Railway Postal Service, which sorted out mail in cars on the way to its destination, which was considered one of the most impressive logistical feats of its time.

Forbes and Vale concentrated on the fact that Bell appeared in all major cities of the country, and that all these cities were connected by long-distance lines. Since the company's main value was its existing subscriber base, they believed that having unparalleled access to existing Bell customers would give them an irresistible competitive advantage in recruiting new customers after the patent expired.

Bell came to new cities not under the name of American Bell, but by issuing a license to recruit its patents to a local operator and buying a controlling stake in this company during the transaction. To further promote and expand the lines connecting city offices, they founded another company, American Telephone and Telegraph (AT & T) in 1885. Weil added to his impressive list of posts the presidency in this company. But probably the most important addition to the company's portfolio was the acquisition in 1881 of a controlling stake in Chicago-based electrical equipment company, Western Electric. Initially, it was founded by rival Bell, Elisha Gray, then she became the main supplier of Western Union equipment to eventually become a manufacturer at Bell.

It was only in the early 1890s, closer to the end of Bell's legal monopoly, that independent telephone companies began to crawl out of the corners into which Bell drove them with a truncheon named US Patent No. 174,465. For the next twenty years, independent companies posed a serious threat to Bell. the parties expanded rapidly in the fight for territory and subscribers. In order to spur the expansion, Bell with a gesture of a conjurer turned his organizational structure inside out, turning AT & T from a private company to a holding one. American Bell was issued according to the laws of the pieces. Massachusetts, who followed the old concept of a corporation as an open public limited liability company, so American Bell had to ask state legislatures to enter the new city. And AT & T, organized according to the liberal corporate laws of New York, had no such need.

AT & T expanded its networks and established or bought companies to consolidate and protect its claims to major urban centers, expanding its ever-growing network of long-distance lines across the country. Independent companies seized new territories with all possible speed, especially in small towns, where AT & T had not yet reached.

During this intense competition, the number of used phones grew at an amazing rate. By 1900, there were already 1.4 million telephones in the USA, against 800,000 devices in Europe and 100,000 in the rest of the world. 60 Americans accounted for one unit. In addition to the United States, only Sweden and Switzerland approached such a density. Of the 1.4 million phone lines, 800,000 belonged to Bell subscribers, and the rest to independent companies. In just three years, these figures rose to 3.3 million and 1.3 million, respectively, and the number of switches was close to tens of thousands.

Number of switches, approx. 1910

A growing number of switches even more burdened central telephone exchanges. In response, the telephone industry has developed a new technology for switching, branching out into two main parts: one to which Bell favored was served by operators. The other, adopted by independent companies, used electromechanical devices to completely eliminate operators.

For convenience, we will call it a fault between manual and automatic switching. But do not let this terminology mislead you. In the same way as with “automatic” cash registers in supermarkets, electromechanical switches, especially their earlier versions, gave an additional load to customers. From the point of view of the telephone company, automation reduced the cost of labor, but from a system point of view, they shifted the paid labor of the operator to the user.

Operator pending

In this era of competition, Chicago was the main Bell System innovation center. Angus Hibbard, general manager of Chicago Telephone, expanded the boundaries of telephony to increase the possibilities offered by a wider user base - and AT & T did not like it very much. But since there was not too much connection between AT & T and the operating companies, she could not directly control it - just look and grimace.

By that time, most of Bell's customers were merchants, business leaders, doctors, or lawyers who paid a fixed amount for unlimited use of the telephone. Few people could afford to pay $ 125 per year, which is equivalent to several thousand dollars today. In order to expand the service to more customers, Chicago Telephone in the 1890s introduced three new offers that had both lower cost and reduced level of service. At first, there was a service with a time counter on the line with access for several persons, the cost of which consisted of a minute-and-minute and very small subscription fee (due to the division of one line between several users). The operator recorded the use of time by the client on paper - the first automatic counter in Chicago appeared only after the First World War. Then there was a service for local switches, with an unlimited number of calls for several quarters around, but with a reduced number of operators per client (and therefore with increased connection time). And finally, there was also a pay phone installed at home or in the client’s office. A five-cent coin was enough to make a call lasting up to five minutes to any place in the city. It was the first telephone service available for the middle class, and by 1906, 40,000 of the 120,000 Chicago telephones were paid.

To keep up with the rapidly growing subscriber base, Hibbard worked closely with Western Electric, whose main factory was also located in Chicago, and specifically with Charles Scribner, its chief engineer. Now nobody knows about Scribner, but then he, the author of several hundred patents, was considered a famous inventor and engineer. Among his first achievements was the development of a standard switch for the Bell system, including a connector for the operator wire, called a jack-knife for resembling a folding pocket knife [jackknife]. Subsequently, this name was reduced to "jack."

Scribner, Hibbard, and their teams reworked the central switch circuit to increase the efficiency of the operators. Signals "busy" and "howler" (meaning that the phone was removed from the lever) freed the operators from having to tell the callers about the error. Small electric lamps showing active calls replaced the valves, which the operator had to put in place each time. The greeting of the operator “hello”, who invited to the conversation, was replaced with “number, please”, which meant only one answer. Due to such changes, the average connection time for local calls in Chicago decreased from 45 seconds in 1887 to 6.2 seconds in 1900.

Typical switchboard with operators, approx. 1910

While Chicago Telephone, Western Electric and other Bell tentacles were working to make communication through the operator fast and efficient, others tried to completely get rid of the operators.

Elmon Brown Strowger

Devices for connecting telephones without human participation have been patented, demonstrated and put into operation since 1879 by inventors from the USA, France, Britain, Sweden, Italy, Russia and Hungary. In the United States alone, by 1889, 27 patents were registered for an automatic telephone switchboard. But, as has often happened throughout our history, the fame for the invention of an automatic switch was unfairly given to one person: Elmon Strowger. This is not entirely wrong, because before him people built disposable devices, treated them like funny things, could not get out of small and slowly growing telephone markets, or simply could not successfully use the idea. The Strowger machine was the first to be implemented on an industrial scale. But it is also impossible to call it “the Strowger machine”, because he himself never built it.

Strowger, a 50-year-old Kansas City schoolteacher who became an entrepreneur, was little like an innovator in an era of ever-increasing technical specialization. The story of the invention of the switchboard has been told many times, and they seem to belong to the realm of myths, and not hard facts. But all of them are connected with Strowger’s discontent with the fact that the operators of his local telephone exchange redirected clients to his competitor. Already not to know whether there was in fact such a conspiracy, and whether Strowger was his victim. Most likely, he himself was not such a good entrepreneur as he considered himself. In any case, it was out of this situation that the idea of ​​a “no girls” phone emerged.

His patent of 1889 described the appearance of a device in which a rigid metal arm replaced an elegant handle of a telephone operator. Instead of a wire with a jack, she held a metal contact capable of moving in an arc and choosing one of 100 different customer lines (either in the same plane, or, in the “twin-engine” version, in ten planes with ten lines each).

The caller controlled the hand with two telegraph keys, one for dozens and one for units. To connect to the subscriber 57, the caller pressed the tens key five times so that the hand moved to the desired group of ten customers, then pressed the unit key seven times to reach the desired subscriber in the group, then pressed the summary key for the connection. On the telephone with the operator, the caller simply needed to pick up the phone, wait for the operator to answer, say “57” and wait for the connection.

The system was not only tedious to use, but also required excessive equipment: five wires from the subscriber to the switch and two batteries for the phone (one for controlling the switch, the other for talking). By that time, Bell had already switched to a centralized battery system, and their newest stations did not have any batteries and only one pair of wires.

Strowger, as they say, built the first model of a switch out of pins stuck in a stack of starched collars. To implement a practical device, he needed financial and technical assistance from several of the most important partners: in particular, businessman Joseph Harris and engineer Alexander Keith.Harris provided Strowger with funding and followed the creation of the Strowger Automatic Telephone Exchange Company, which produced the switches. He wisely decided to place the company not in Kansas City, but in his home in Chicago. Due to the presence of Western Electric was at the center of telephone engineering. Among the first engineers hired was Keith, who transferred to a company from the world of electricity generation and became technical director of Strowger Automatic. With the help of other experienced engineers, he turned the rough concept of Strowger into a precise tool, ready for mass production and use, and guided all the major technical improvements of this tool in the next 20 years.

Of these improvements, two were particularly important. The first is the replacement of a set of keys with one dial-up disk, which automatically generated both pulses that moved the switch to the desired position and the connection signal. This made subscriber equipment extremely simplified and became the default mechanism for managing automatic switches until Bell introduced voice dialing to the world in the 1960s. Automatic telephone has become synonymous with disk telephone. The second is the development of a two-connected switching system, which allowed 1000, and then 10,000 users, to connect with each other, dialing 3 or 4 digits. The switch of the first level chose one of ten or one hundred switches of the second level, and that switch chose the right one from 100 subscribers. This allowed the automatic switch to become competitive in big cities,where thousands of subscribers lived.

Strowger Automatic installed the first commercial switch in Laporte, Indiana in 1892, serving eighty subscribers of the independent Cushman Telephone Company. The former Bell subsidiary who worked in the city successfully got out of it, losing a patent dispute with AT & T, which gave Kushman and Strowger a great opportunity to take his place and lure his customers. Five years later, Keith oversaw the first installation of a two-tier switch in August, Georgia, serving 900 lines.

By this time, Strowger retired and lived in Florida, where he died several years later. His name was excluded from the name of Automatic Telephone Company, and it became known as Autelco. Autelco was the main supplier of electromechanical switches in the United States and most of Europe. By 1910, automatic switches served 200,000 US subscribers to 131 telephone exchanges, almost all of which were built by Autelco. Each was owned by an independent telephone company. But 200,000 were a small fraction of America’s millions of telephone subscribers. Even the majority of independent companies have followed in the footsteps of Bell, and Bell itself has not yet considered seriously the possibility of replacing its operators.

General management

Bell opponents tried to explain the company's commitment to the use of operators by some malicious motives, but their accusations are hard to believe. There were several good reasons for this, and one that seemed reasonable at the time, but in retrospect looking wrong.

Bell needed to start developing its own switch. AT & T did not intend to pay Autelco for its telephone exchanges. Fortunately, in 1903, she acquired a patent for a device developed by the Lorimer brothers from Brantford, Ontario. It was in this city that the parents of Alexander Bell settled after leaving Scotland, and where for the first time the idea of ​​the phone came to his mind when he stayed there in 1874. Unlike the Strowger switch, the Lorimer device used reverse pulses to move the selector lever — that is, electrical pulses came from the switch, each of them switching the relay in the subscriber's equipment, causing it to count down from the number specified by the subscriber on the lever to zero.

In 1906, Western Electric loaded two separate teams with the development of switches based on the Lorimer idea, and the systems they created — panel and swivel — formed the second generation of automatic switches. Both of them replaced the lever with a conventional dial, transferring the pulse receiver inside the central station.

More important for us is that the mechanics of Western Electric's switchgear — carefully described by phone historians in great detail — were relay circuits used in switching control. And historians have only mentioned this in passing.

And it’s a pity, because the appearance of control relay circuits has two important consequences for our history. In the long run, they inspired the idea that switch combinations can be used to represent arbitrary arithmetic and logical operations. The implementation of these ideas will be the topic of the next article. First, they bypassed the last serious engineering problem of automatic switches - the ability to scale to service large urban areas in which Bell had thousands of subscribers.

The method of scaling Strowger switches used by Alexander Keith to switch between 10,000 lines could not be scaled too much. If you continue to increase the number of levels, then each call needed to devote too much equipment. Bell engineers have called the alternate scaling mechanism the sender. He stored the number dialed by the caller in the register, then translated this number into arbitrary (usually non-numeric) codes that controlled the switches. This made it possible to set up switching much more flexibly — for example, calls between switches could be redirected through the central station (which did not correspond to any digit in the dialed number), instead of connecting each switch in the city with all the others.

Apparently, Edward Molina, a research engineer at AT & T Traffic Division, first came up with the "sender". Molina was noted for innovative research that applied mathematical probability to the study of telephone traffic. These studies led him around 1905 to the idea that if call forwarding was decoupled from the decimal number dialed by the user, then the machines would be able to use the lines much more efficiently.

Molina mathematically demonstrated that the distribution of calls to larger groups of lines allowed the switch to use a larger volume of calls, while maintaining the probability of a busy signal at the same level. But Strowdger's switches were limited to a hundred lines, chosen by two numbers. Switches for 1000 lines based on three digits were considered ineffective. But the movements of the selector, controlled by the sender, do not necessarily have to coincide with the dialed numbers. Such a selector could choose from 200 or 500 lines available to pivot and panel systems, respectively. Molina proposed a device that records and translates calls, constructed from a mixture of relays and ratchets, but when AT & T was ready to embody panel and pivoting systems,other engineers have already come up with faster “senders” based on relays alone.

The number-diverting device was Molina’s patent No. 1,083,456 (sent in 1906, approved in 1914)

There was a small step from the “sender” to the combined control. Teams at Western Electric realized that it was not necessary to fence the sender for each subscriber or even for each active call. A small number of control devices could be divided between all lines. When a call arrived, the sender switched on for some time and recorded the dialed digits, worked with the switch to redirect the call, then disconnected and waited for the next one. With a panel switcher, a sender, and a combined control, AT & T received a flexible and scalable system capable of meeting even the needs of the massive networks of New York and Chicago.

Relay in panel switch

But despite the fact that the company's engineers have rejected all technical objections to telephony without operators, the AT & T management still doubted. They were not sure that users would cope with the set of six- and seven-digit numbers needed for automatic switching in large cities. At that time, callers dialed up to subscribers of local switches, giving the operator two details - the name of the desired switch and (usually) a four-digit number. For example, a client from Pasadena could get through to a friend from Burbank, saying, “Burbank, 5553.” Bell management believed that replacing Burbank with a random two- or three-digit code would lead to a large number of incorrect dial-ups, user frustration and poor service quality.

In 1917, William Blowwell, an AT & T worker, proposed a method for eliminating these problems. Western Electric could in the manufacture of the device for the subscriber to print two or three letters next to each digit dial. The telephone directory would display the first few letters of each switch, corresponding to its digital year, in capital letters. Instead of memorizing a random numeric code for the desired switch, the caller would simply spell the number: BUR-5553 (for Burbank).

The Bell 1939 dialing dial with the number for Lakewood 2697, that is 52-2697.

But even when there were no objections to switching to automatic switches, AT & T still had no technical or operational reasons for avoiding the successful method of connecting calls. She pushed for this only war. The gigantic increase in demand for industrial goods constantly raised the cost of labor for workers: in the United States from 1914 to 1919 it almost doubled, which led to an increase in wages in other areas. Suddenly, the key point for comparing switches that are operated by operators or automatically, was not technical or operational, but financial. Given the growing cost of operator pay, by 1920 AT & T decided that it was no longer possible to resist mechanization and gave the order to install automatic systems.

The first such system with panel switches in Omaha, Nebraska, was launched in 1921. It was followed by the New York switch in October 1922. By 1928, 20% of the AT & T switches were automatic; by 1934 - 50%, by 1960 - 97%. Bell closed the last telephone exchange with operators in Maine in 1978. But operators were still needed to organize long distance calls, and in this post they were replaced only at the end of the Second World War.

Based on technology and business stories that are popular in our culture, one could easily assume that the awkward AT & T barely escaped destruction by agile small independent companies, eventually switching to an obviously more advanced technology that was first tested by small enterprises. But in fact, AT & T paid for the threat posed by independent companies ten years before the automation of telephone exchanges.

Triumph bell

Two events in the first decade of the 20th century convinced a large part of the business community that no one could overcome the Bell System. The first was the failure of an independent company United States Independent Telephone Company of Rochester from New York. The United States Independent decided for the first time to build a competing communications network over long distances. But they were unable to enter the critical market of New York and went bankrupt. The second was the collapse of the independent company Illinois Telephone and Telegraph, which tried to enter the Chicago market. Other companies not only could not compete with AT & T's long-distance communications, but also seemed to be unable to compete with it in large urban markets.

Moreover, the approval by the Chicago leadership of Bell’s operating company (Hibbard’s Chicago Telephone) in 1907 made it clear that city governments would not try to increase competition in the telephone business. A new economic concept of natural monopoly emerged - the belief that for some types of public services, combining them with one supplier was a profitable and natural result of market development. According to this theory, the correct reaction to a monopoly was its public regulation, and not imposed competition.

" Commitment Kingsbury " in 1913 confirmed the receipt from the federal government the right to work of Bell. At first it seemed that the progressive administration of Wilsonskeptical of massive corporate combining can break the Bell System or somehow curb its dominance. That's what everyone thought when the Attorney General under Wilson, James MacReynolds, reopened the suit against Bell, filed according to Sherman's first antitrust act , and set aside by his predecessor. But AT & T and the government soon reached an agreement signed by the company's vice president, Nathan Kingsbury. AT & T agreed to sell Western Union (in which a few years before it bought a controlling stake), to stop buying independent telephone companies and connecting independent companies through its long-distance network at reasonable rates.

AT & T seemed to have a serious blow to its ambitions. But the result of Kingsbury's commitment only confirmed its power in the national telephony. Cities and states have already made it clear that they will not forcefully restrict the monopoly on telephony, and now they have joined the federal government. Moreover, the fact that independent companies gained access to a long-distance communication network guaranteed that this network would remain the only such network in the United States until the appearance of microwave networks after half a century.

Independent companies became part of a huge machine, in the center of which was Bell. The ban on the acquisition of independent companies was canceled in 1921, since it was a large number of such companies seeking to sell to AT & T, the government requested. But many independent companies survived and even flourished, in particular, General Telephone & Electric (GTE), which bought Autelco as a competitor to Western Electric, and had its own collection of local companies. But they all felt the gravitational pull of the star Bell, which revolved around.

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