History of the development of communication systems. History of the creation of electrical networks and systems

At the dawn of human society, communication between people was very scarce. A branch stuck into the ground indicated in which direction and at what distance the people had gone; especially laid stones warned of the appearance of enemies; notches on sticks or trees reported hunting prey, etc. There was also primitive transmission of signals over a distance. The messages, encoded in the form of a certain number of shouts or drum beats with a changing rhythm, contained one or another information.

In the tenth volume “ General history” the ancient Greek historian Polybius (c. 201–120 BC) described a method of transmitting messages over a distance using torches (torch telegraph), invented by the Alexandrian scientists Cleoxenes and Democletus.

In 1800, the Italian scientist A. Volta created the first chemical current source. This invention enabled the German scientist S. Semmering to build and present a project for an electrochemical telegraph to the Munich Academy of Sciences in 1809. In October 1832, the first public demonstration of the electromagnetic telegraph by the Russian scientist P.L. Shilling. In the same year, with the help of the Schilling telegraph, communication was established between the Winter Palace and the Ministry of Railways.

A real revolution in the field of telecommunications by wire was made by the Russian academician B.S. Jacobi and the American scientist S. Morse, who independently proposed a writing telegraph.

In 1841 B.S. Jacobi commissioned a line equipped with a writing telegraph and connecting Winter Palace with the General Staff. Two years later, a similar line with a length of 25 km was built between St. Petersburg and Tsarskoe Selo. In 1850 B.S. Jacobi designed the first direct-printing machine. In June 1866, a cable was laid through Atlantic Ocean. Europe and America found themselves connected by telegraph.

The birth of the telegraph gave impetus to the appearance of the telephone. Since 1837, many inventors have tried to transmit human speech over a distance using electricity. In 1876, American inventor A.G. Bell patented a device for transmitting speech over wires - the telephone. In 1878, the Russian scientist M. Makhalsky designed the first sensitive microphone with carbon powder.

At first, they were used for telephone communication. telegraph lines. A special two-wire telephone line was designed in 1895 by Professor P.D. Voinarovsky and built in 1898 between St. Petersburg and Moscow.

In 1886, Russian physicist P.M. Golubitsky developed new scheme telephone connection. According to this scheme, the microphones of subscriber telephone sets received power from one (central) battery located at the telephone exchange. The first telephone exchanges in Russia were built in 1882–1883. in Moscow, St. Petersburg, Odessa.

The first public demonstration of the A.S. device Popov for receiving electromagnetic waves took place on May 7, 1895. This day went down in history as the day of the invention of radio.

Employees of the Nizhny Novgorod laboratory created in 1918 (headed by M.A. Bonch-Bruevich) already in 1922 built the world's first radio broadcasting station with a power of 12 kW in Moscow.

In 1935, an ultrashort wave radio link, which was later called the “radio relay link,” came into operation between New York and Philadelphia.

From now on, chains of radio relay lines stretched to all corners of the globe. The construction of the first radio relay line in our country was carried out in 1953 between Moscow and Ryazan.

“Beep...beep...beep.” These signals were heard on October 4, 1957 by the whole world. The era of space exploration has arrived. A very short period of time separates us from this date, and space orbits Thousands of artificial satellites have already been launched, serving mankind regularly.

On April 23, 1965, it was launched in the USSR artificial satellite Earth "Molniya-1", on board of which there was a transceiver relay station.

In 1960, the world's first laser was created in America. This became possible after the appearance of the works of Soviet scientists V.A. Fabrikanta, N.G. Basov and A.M. Prokhorov and the American scientist Charles Townes, who received the Nobel Prize.

Lasers began to be “taught” to transmit information over a distance soon after their invention. The first laser communication lines appeared in the early 60s of this century. In our country, the first such line was built in 1964 in Leningrad.

Muscovites are familiar with such corners of the capital as the Lenin Hills and Zubovskaya Square. In 1966, a red thread of laser light appeared between them. It connected two city automatic telephone exchanges located at a distance of 5 km from each other.

In 1970, the American company Corning Glass Company produced ultra-pure glass. This made it possible to create and implement optical communication cables everywhere.

In 1947, the first mention of the pulse-code modulation (PCM) system developed by Bell appeared. The system turned out to be cumbersome and ineffective. It was only in 1962 that the first commercial transmission system, PKM-24, was put into operation.

Modern trends in the development of telecommunications

In subsequent years, communications developed along the path of digitalization of all types of information. This has become a general trend, providing cost-effective methods not only for its transmission, but also for distribution, storage and processing.

The intensive development of digital transmission systems is explained by the significant advantages of these systems compared to analogue transmission systems: high noise immunity; weak dependence of transmission quality on the length of the communication line; stability of electrical parameters of communication channels; efficiency of using bandwidth when transmitting discrete messages, etc.

In 2002, the development of local telephone communications was carried out mainly on the basis of modern digital telephone exchanges, which made it possible to improve the quality and expand the range of services provided. Capacity ratio of digital stations from the total installed capacity of the local telephone network in 2002. amounted to about 40% versus 36.2% in 2001. As of January 1, 2003, there were about 195 thousand long-distance and local payphones operating on Russian networks, including 63 thousand universal ones. The number of payphones increased by 13% and amounted to 127.5 thousand. The increase in the number of main telephone sets of the local telephone network amounted to 1.8 million units, mainly due to telephone sets installed among the population. The total number of cellular mobile communications subscribers in Russia at the end of 2002 was 17.7 million, the increase in the subscriber base compared to 2001 was 2.3 times. In 2002, over the year, the Russian computer park increased by 20% compared to 2001. The number of regular Internet users increased by 39% and reached 6 million people. The volume of the domestic IT market grew by 9% and amounted to more than 4 billion. dollars. In 2002, more than 50 thousand km of cable and radio relay communication lines, 3 million numbers of automatic telephone exchanges, more than 13 million mobile telephone numbers, as well as over 70 thousand long-distance and international channels were put into operation.

The mobile radio network is developing at a particularly rapid pace in the world and in our country. By the number of subscribers of the mobile communication system, one can already judge the level and quality of life in a given country. In this sense, the growth rate of mobile subscribers in Russia (almost 200% per year) is an indicator of the growth in the well-being of society.

Based on the macroeconomic indicators of the development of the Russian Federation, defined in the Main Directions of the Social and Economic Policy of the Government of the Russian Federation for the long term, the telecommunications services market by 2010 will be characterized as follows (Table 1).

Table 1. Indicators of development of telecommunications in Russia for the period up to 2010

Humanity is moving towards the creation of a Global Information Society. Its basis will be the Global Information Infrastructure, which will include powerful transport communication networks and distributed access networks that provide information to users. Globalization of communications and its personalization(bringing communication services to every user) - these are two interrelated problems that are being successfully solved at this stage of human development by telecommunications specialists.

The further evolution of telecommunications technologies will go in the directions of increasing the speed of information transfer, intellectualizing networks and ensuring user mobility.

High speeds. Necessary for transmitting images, including television, integrating various types of information in multimedia applications, organizing communications of local, city and territorial networks.

Intelligence. It will increase the flexibility and reliability of the network and make it easier to manage global networks. Thanks to the intellectualization of networks, the user ceases to be a passive consumer of services, turning into an active client - a client who can actively manage the network himself, ordering the services he needs.

Mobility. Advances in miniaturization electronic devices, reducing their cost creates the prerequisites for the global spread of mobile terminal devices. It does real task providing communication services to everyone anytime and anywhere.

In conclusion, we note that the amount of information transmitted through the information and telecommunications infrastructure of the world doubles every 2-3 years. New branches of the information industry are emerging and successfully developing, the information component of the economic activity of market entities and the influence of information technologies on the scientific, technical, intellectual potential and health of nations is significantly increasing. The beginning of the 21st century is considered as the era of the information society, which requires effective development creation of a global information and telecommunications infrastructure, the pace of development of which should be faster than the pace of development of the economy as a whole. At the same time, the creation of the Russian information and telecommunications infrastructure should be considered as the most important factor in the rise of the national economy, the growth of business and intellectual activity of society, and the strengthening of the country’s authority in the international community.

Ministry of Education and Science of the Russian Federation

State educational institution of higher professional education

Department of Civil Law

course work on TELECOMMUNICATIONS LAW

"Development of telecommunication networks"

Performed:

_____________________

Checked by: Scientific director

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MOSCOW 2010

Introduction

1. History of the development of telecommunication networks

1. The beginning of the history of telephony

2. Development of long-distance telephone communications

3. Reconstruction and automation of telephone networks

1. Classification of telecommunication networks

2. Principles of building long-distance telephone communications

3. Principles of building intrazonal telephone communications

2.6 Construction of a wired broadcasting network

Conclusion

Bibliography

INTRODUCTION

With the invention of the electric telegraph in 1835, a new era began in the history of mankind - the era of telecommunications. In less than 200 years, telecommunications technology has come a long way - from bulky and clumsy devices that could only be used by government organizations and a few of the wealthiest individuals, to a global infrastructure that provides communications throughout the globe between its most remote corners. The enormous speed with which electromagnetic waves propagate makes it possible to cover distances of tens of thousands of kilometers in tiny fractions of a second, transmitting all types of information: sound, still and moving images, computer data, etc.

Initially, electrical communication was wired. Only at the end of the 19th century was the possibility of communication without wires discovered and used, through electromagnetic waves propagating in free space. To date, wireless technologies have become extremely widespread. However, despite the use of the most modern means and methods of signal processing, wireless communications are inferior in throughput to cable lines and are unlikely to ever surpass them. This is due to the fact that the electromagnetic signal propagating in a closed guide system (cable) is in much more favorable conditions than a radio signal in open space. It is practically unaffected by signals from other lines, it is not affected by weather conditions, distortion due to multipath propagation, etc.

At the same time, the equipment cable line Communications are an extremely labor-intensive and expensive undertaking. Many kilometers of cable must be buried in the ground or laid through cable ducts. Additional difficulties arise when overcoming water obstacles, roads and railways. It should also be noted that for most of the history of telecommunications, exclusively metal cables were used, which were made from expensive metals such as copper and lead.

All these problems, already at the very early stages of the development of wired communications, led to the need to increase the efficiency of using linear cable structures by simultaneously transmitting several signals over one pair of wires. The development of such methods laid the foundation for the creation of multiplexing or multiplexing equipment. Densification technologies have gone through several stages in the course of their development and have now ensured the creation of a powerful global network of standard channels and paths, that is, the so-called primary, or transport, network.

1. History of the development of communication networks

The beginning of the history of telephony

The advent of the telephone for the first time opened up the possibility of direct negotiations between subscribers. However, this advantage was not immediately appreciated. First, telephone communication was hyped before reliable phones and microphones were released. And secondly, potential subscribers - business people - successfully used another type of communication - the telegraph, appreciating it for its ability to transmit documentary records. Therefore, the arrival of telephony in Russia has slowed down somewhat. The first small private telephone exchanges began operating only in 1880, two years after the invention of the Bell tube. [ 1 ] However, even then they began to think about creating city telephone networks.

September 25, 1881 Russian government approved the "Basic conditions for the arrangement and operation of urban telephone messages in Russia." According to the document, the right to construct and operate was granted to the entrepreneur for a period of 20 years, after which telephone facilities were to be transferred free of charge to the government. The first contract was concluded on November 1, 1881 between the Ministry of the Interior, which was in charge of communications, on the one hand, and a private entrepreneur, engineer von Baranov, on the other. However, von Baranov did not build the network, but sold his rights to the International Bell Telephone Company. The entire initial history of telephony in Russia is connected with it. The Bell company had a monopoly in the operation of telephone exchanges in large cities for many years.

The commissioning of the first stations took place in 1882 almost simultaneously in St. Petersburg, Moscow, Odessa and Riga. A few years later, in 1885-1886, telephone networks were equipped and opened in Nizhny Novgorod, Libau, Revel, Rostov-on-Don and Baku. [2]

The first telephone exchanges of the Bella company in Russia worked with single-wire subscriber lines and were carried out using Hilleland system boards with a capacity of 50 numbers each. This device was a manual switch with a vertical panel and a horizontal table on which longitudinal and transverse brass strips 0.5 mm thick were located. These strips were connected by a plug-in plug. Between the vertical board and the horizontal table there were 50 (one for each number) calling valves arranged in two rows. Subscriber lines were connected to terminals on back side switchboard. Each of them was connected to the electromagnet of the corresponding calling valve and the corresponding strips on the horizontal table and vertical panel. As the station expanded, each Hilleland board included connecting lines to communicate with other station boards. For example, Moscow station to end of the 19th century century had 16 boards with 90 connecting lines each.

Subscriber devices at that time consisted of a Bell tube, a Blake microphone, a Hilleland inductor and bell, and a battery of Leclanche elements. These telephone sets, called Bell-Black, caused a lot of criticism, in particular, because of the inconvenient placement of the microphone (it was built into the body of the device, and the speaker had to bend over), as well as because of the high mutual induction of single-wire subscriber lines and imperfect lever system, which often failed.

Taking advantage of its monopoly right, the Bella company set an unprecedentedly high fee for using the telephone - 250 rubles. per year and, having provided themselves with extremely high profits, did not seek to invest in improving the built system, even despite numerous complaints. Often the subscriber could not connect with the person being called for several hours.

Several telephone operators worked simultaneously at each station. One of them, having received a call signal, asked the subscriber with whom he wanted to establish a connection. If the required number was included in another switchboard, the first telephone operator loudly announced this to the other. She, in turn, making sure that the number was not busy, connected it to a free trunk line leading to the first switchboard, and loudly notified its telephone operator about this. And only after that the telephone operator who received the ringing signal connected the subscriber. Due to the loud conversations of the telephone operators, which created noise and confusion at the station, connection errors often occurred.

During the 20-year concession period, the company only installed lightning protection devices and replaced outdated Gileland boards with cabinet-type switches. They were equipped with individual subscriber sockets and calling blankers. Each switch was designed for 200 single-wire subscriber lines, which made it possible to expand the station and reduce the number of telephone operators. In the fall of 1901, by the end of the Bella company's concession, the St. Petersburg network served 3.8 thousand subscribers, the Moscow network - 2.86 thousand.

Development of long-distance telephone communications

The concept of long-distance telephone communication is used to refer to telephone communication between subscribers different zones numbering, and thus includes the concepts of long-distance and international communications. [3]

The development of long-distance telephone communication in our country began in the 80s years XIX century, earlier than in some other European countries. The first intercity line was built between St. Petersburg and the Tsar's residences in Gatchina (1882), Peterhof (1883) and Tsarskoye Selo (1885). In 1885, Moscow industrialists financed the construction of single-wire steel telephone lines between Moscow and Bogorodsk, Pushkin, Khimki, Odintsovo, Kolomna, Podolsk and Serpukhov. Then the connection with these cities was called “suburban”. The operation of genuine long-distance communications began after the improvement of methods of simultaneous telegraphy and telephone. The credit for this goes to telegraph specialist G. G. Ignatiev and engineer E. I. Gvozdev.

G. G. Ignatiev invented a device that separates telegraph and telephone currents using capacitors and inductors connected to the circuit. His system was put into trial operation in 1881 on a 14.5 km long overhead line connecting the camps of the Kyiv Military District.

E.I. Gvozdev proposed to concentrate sets of capacitances and inductances of different parameters at stations and developed schemes for parallel and sequential connection of them in various cases. The Telephone Partnership he created in 1888-1889. on the Rybinsk-Bologoevskaya Railway successfully tested Gvozdev’s devices for simultaneous telegraphy and telephony over a distance of 295 km.

In 1898, under the leadership of engineer A. A. Novitsky, the St. Petersburg - Moscow telephone line was built. At that time it was the longest in Europe. Switches for the first long-distance station were purchased in Belgium. Similar stations appeared in Odessa, Warsaw, Riga and Lodz over the next 20 years. [ 4 ]

By 1913, telephone communication via copper two-wire lines was established between Moscow and Kharkov, Ryazan, Nizhny Novgorod and Kostroma, between St. Petersburg and Revel, Helsingfors and between Baku and Tiflis. In total, 87 long-distance telephone lines were in operation at that time.

Until 1917, the only type of long-distance switching equipment produced in Russia were the “Zemstvo” switches of the Russian joint-stock company L. M. Erickson and Company.

Currently, the long-distance telephone network is analog and is built on a hierarchical principle and has two levels of hierarchy. The first level is the terminal telephone exchanges, the second is the automatic switching nodes (ASK). The strategic basis for the development of long-distance communications in Russia is the creation of a digital non-hierarchical long-distance network. Planned transition from hierarchical structure networks to a non-hierarchical structure with dynamic traffic control. In the new structure, it is assumed that each ATE will have at least two directions to UAC transit nodes, and, as a maximum, can be connected to all UAC transit nodes of the network. It is assumed that the entire intercity network will participate in the distribution of traffic during busy hours (PHH) for any region of the country. Since there are 11 time zones on the territory of Russia, the CHNN, for example, in Central region will coincide with the time of least load for the Far East and East Siberian regions. As a result, it will be possible to use the network in remote areas to reduce the load.

Reconstruction and automation of telephone networks

The Bell International Telephone Company's concession for the construction and operation of telephone networks in Russia ended in 1901. The government announced bidding for a new 18-year period, setting a low subscription fee as one of the mandatory conditions. As a result of the bidding, the city government received the concession in St. Petersburg, the Swedish-Danish-Russian joint-stock company in Moscow, and private entrepreneurs in other cities.

The new owners began operating the networks with their reconstruction. Since the creation of the first telephone, a number of technical innovations have been developed that Bella ignored, which delayed the development of networks. In particular, previously metropolitan telephone networks used local battery (MB) systems. As the capacity of city stations grew, monitoring the status of power supplies became increasingly difficult. In 1886, Pavel Mikhailovich Golubitsky, having studied the possibility of organizing power supply for all subscriber devices from a single source at the telephone exchange, invented a microtelephone communication system with batteries concentrated in the central bureau. This system was first used in Paris. In Russia, it was put into operation in 1904 in Moscow and St. Petersburg at new telephone exchanges. [ 5 ]

In 1901, the Russian Society of Electricians completed a project for the reconstruction of the St. Petersburg telephone network. It included installation on new station switches of a two-group system with the ability to include up to 20 thousand subscribers in each group. The construction of the new station and the supply of equipment for it was undertaken by N. K. Geisler and Company.

The project for the reconstruction of the Moscow city network, the construction of a new station and the supply of equipment was carried out by the Swedish company L. M. Ericsson, operating through the Swedish-Danish-Russian joint-stock company. The project involved the installation of distribution system switches at a new station with the possibility of including multiple switches in the field with up to 60 thousand slots.

By the beginning of 1914, the capacity of the St. Petersburg telephone network was increased to 49,860 numbers, the Moscow one - 44,293. By 1917, Moscow and St. Petersburg accounted for half of all operating telephones in Russia - 232 thousand.

Until the 1930s, Russian telephone networks were equipped with manual telephone exchanges. At the initial stage of telephony development, they fully answered necessary requirements. But with the growth in the number of subscribers, zoning of telephone networks began - the establishment of stations in each district of the city. The use of so-called "manual" stations did not fit well into this process due to a number of significant disadvantages. For each external connection, two telephone operators were involved, which affected the quality of service. In addition, stations were connected according to the “each to each” principle, and with a large number of regional stations, the use of interstation connecting line equipment was reduced. To this should be added the high costs of cable, and therefore financial resources. These and some other shortcomings could be eliminated only by automating telephone communications.

Experiments on automation of communication have been carried out since the very beginning of the spread of the telephone. The first patent for a simple automatic telephone exchange (ATS) was received in 1879 by a group of American inventors. Two years later, the authors improved their pulse relay system for transmitting pulses. Significant contributions to the automation of telephone communications were made by Russian inventors K. A. Mossitsky, M. F. Freidenberg, and the American A. B. Strowger.

K. A. Mossitsky first put forward the idea of ​​a relay (without finders) automatic telephone exchange in 1887 and developed a station diagram for six numbers. But this was not yet a PBX in the modern sense, since the switching of connections, although carried out without telephone operators, was controlled by subscribers. The caller sent the call sign of the called subscriber through the station, and this signal was sent to all telephone sets included in the station. [6]

A. B. Strowger in 1889 patented a finder with two movements of contact brushes - lifting and rotating - the prototype of a stepper telephone finder.

The basis for the design of automatic telephone exchanges was the pre-finder created in 1895 by M. F. Freidenberg and his principle of free search. The Russian inventor, working on communication automation, sought to find a solution that would make the PBX more cost-effective than a manual station of the same capacity. This was hampered by the use of bulky and expensive finders with multiple fields. Freudenberg came to the conclusion that in a system consisting of 10 thousand subscribers, it is enough to ensure that any 500 pairs of subscribers can simultaneously communicate with each other instead of 5000 pairs, as was envisaged for previously patented equipment. He wrote: “In this invention of mine, I appropriately provided for the use of this opportunity and, thus, achieved a very significant reduction in the cost of the device” (Roginsky V.N. Inventor of the automatic telephone communication system. Communication Bulletin. Communication Engineering, 1950, No. 7 , 8).

In 1896, M. F. Freudenberg created a linear finder with 1 thousand lines with a common multiple field for a group of finders, and then introduced group finders. The model of the automatic telephone exchange of the last system, the so-called machine one, was successfully tested in Paris in 1898.

The first automatic telephone exchange was created in 1900 in the USA. In Russia, automatic telephone exchanges with a machine finder began to spread only in 1929, with the opening of the first automatic telephone exchange with a capacity of 6 thousand numbers in Rostov-on-Don. In 1930, the Zamoskvoretskaya ATS with a capacity of 8 thousand numbers and the Bauman ATS with a capacity of 7 thousand numbers were put into operation in Moscow. The construction of these stations was carried out by the Leningrad plant "Krasnaya Zarya" according to the technical and technological documentation of the Swedish company "L. M. Ericsson". She was also involved in project development and construction. During the same period, automatic telephone exchanges were opened in Novosibirsk, Tashkent, Smolensk, Leningrad and other cities. [7]

During the Great Patriotic War, automation of telephone networks in Russia was suspended. One of the reasons was that the equipment of the only plant in the country for the production of automatic telephone exchanges - "Red Dawn" - was significantly damaged during the evacuation. No new automatic telephone exchanges were built, and existing ones did not receive spare parts.

The next stage in the improvement of automatic telephone exchanges in Russia began in 1947, when domestic specialists developed a new PBX system - ten-step-step (ATS-47). Its introduction into operation took place in 1949. The main switching elements of the automatic telephone exchange of the ten-step system were stolinear lifting-rotational finders (DSHI-100), rotary finders (SHI-11) and flat telephone relays (RPN).

And the global telephone industry at that time was working on creating more advanced telephone exchanges. To control the automatic telephone exchange, contactless switching elements were used - electronic and ion lamps, cathode ray tubes, semiconductor devices, etc. In 1954, a mechanical-electronic automatic telephone exchange with 2 thousand numbers, proposed by Belgian engineers, was put into operation in Oslo. In their project, they used a Crossbar type coordinate connector, developed in 1913 by the American J. Reynolds and improved in 1919 by the Swedish engineer G. Betulander.

Also in 1954, a prototype of a telephone exchange built entirely on electronic devices was tested in England. Thus began a new era of telephony - electronic.

1. Classification of communication networks

   1. Communication networks as part of infrastructure

The basis for the development of telecommunications in the USSR was the Nationwide Unified Automated Communications Network (EASC), which ensured the functioning of telephone and telegraph transmission and the reception of newspaper pages, and the transmission of radio and television data. [ 8 ]

During the period of perestroika, work was carried out to transform the EASC network into the Interconnected Communications Network of the Russian Federation (ICC RF), taking into account the structural transformations of the country and the development of the latest technical means.

Communications of the Russian Federation as part of the country's infrastructure is a set of networks, services and communications equipment located and operating on the territory of the country. It is designed to meet the needs of the population, public authorities and administration, defense, security, law and order, as well as users of all categories in telecommunication services.

Structurally, the Armed Forces of the Russian Federation is a hierarchical system and includes three levels. The first level is the primary network, the second level is the secondary network, the third level is formed by telecommunication systems (services) of a certain type, depending on the services provided to subscribers.

The primary BSN network is a collection of nodes, transmission lines, standard physical circuits, typical transmission channels and BSN network paths. The primary network provides transmission channels and physical circuits to the secondary networks.

Based on standard transmission channels and physical circuits of the primary network, various secondary networks (telephone, telegraph, data transmission, newspaper transmission, TV and radio program distribution networks) are organized with the help of nodes and switching stations. Secondary networks provide transportation, switching, and distribution of signals in telecommunication services.

On the basis of secondary circuits, telecommunication systems are organized, which are a set of technical means that carry out telecommunications of a certain type and include a corresponding secondary network. A telecommunication system may include one or more telecommunication services and one or more telecommunication networks.

A telecommunication service is an organizational and technical structure based on a communication network (or a set of communication networks) that provides communication services to users in order to meet their needs for a specific set of telecommunication services. There are two types of telecommunication services: bearer services and teleservices (communication services).

The transport service only provides the ability to transmit signals between network interfaces. Endpoints are not included in the migration services.

The teleservice provides the full implementation (including the function of terminal devices) of the capabilities of a certain type of communication between users. The teleservice is organized on the basis of the transport service and terminal devices. Examples of teleservices are telephone, telex, and bureaufax services. The architecture includes terminal devices located at the user's location as part of the corresponding teleservice.

In addition to the accepted division of BSN networks into primary and secondary, another two-level division is possible: into a transport network and an access network.

The transport communication network consists of long-distance and zonal (regional) communication networks. The access network (subscriber network or subscriber access network) is a local network. The transport network is designed for the transmission of high-speed (broadband) message flows and their accumulation.

The access network consists of subscriber lines (on metal or optical cables or radio channels) with subscriber terminal devices of local switching stations connected to them, connecting their transmission lines and transmission lines to transport network nodes.

Use of technical means on the primary public network

The main means of digitalization of the primary network should be digital joint ventures, ensuring the formation of the following digital channels and group digital paths:

Main digital channels 64 kbit/s;

Primary digital channels and digital group paths 2048 kbit/s;

Secondary digital channels and digital paths 8448 kbit/s;

Tertiary digital channels and digital group paths 34368 kbit/s;

Quaternary digital channels and digital group paths 139264 kbit/s;

SDH group digital paths of the first level 155520 kbit/s;

SDH group digital paths of the fourth level 622080 kbit/s;

SDH group digital paths of the sixteenth level 2488320 kbit/s.

Based on territorial characteristics and purpose, primary and secondary networks are divided into main networks (long-distance networks for secondary networks), intrazonal (zonal) and local networks, as well as international networks.

Backbone communication networks are technologically interconnected long-distance telecommunication networks formed between the center of the Russian Federation and the centers of the constituent entities of the Federation, as well as the centers of the constituent entities of the Federation among themselves.

Zonal (regional) communication networks are technologically interconnected telecommunication networks formed within the territory of one or several constituent entities of the Federation.

Local communication networks are technologically interconnected telecommunication networks formed within administrative or otherwise defined territories that are not related to regional communication networks. Local networks are divided into urban and rural.

International communication networks are telecommunication networks that are technologically interconnected with the communication networks of foreign countries and are managed by economic entities that have been granted the rights of international operators.

Currently, the structure of the VSS includes the following public telecommunication systems: telephone communication (STfS), telegraph communication (STgS), facsimile communication (SFS), newspaper transmission (SPG), data transmission (SPD), distribution of sound broadcasting programs (SRPDV) , distribution of television broadcasting programs (SRPTV).

The development of networks of the Russian Air Transport Network provides for a gradual transition to a two-level structure of communication organization: a transport network and an access network (subscriber network).

Backbone, intra-zonal and part of local digital overlay primary networks are the basis of the transport digital communication network of Russia. Local and primary networks in the “local node - terminal device” section, in accordance with the new terminology, are an access network. [ 9 ]

2.2 Principles of building a long-distance telephone network

A long-distance telephone network is a set of long-distance stations, terminal and terminal-transit automatic switching nodes and communication channels between them.

The basis for building a long-distance telephone network is the principle of territorial division, taking into account:

Borders of territories and structure of the backbone primary network;

Administrative division of the territory:

Technical and economic indicators.

This principle, if necessary, can be changed with the emergence of new administrative entities, the creation of economic zones, etc.

The long-distance telephone network is built according to the following principles:

The country is divided into telephone territories. In each territory, an automatic switching node - ASC or a terminal transit station - TTS, performing the role of ASC, is organized. Transit connections of telephone channels are carried out at UAC and OTS. All UAKs and OTNs must be connected to each other by bundles of telephone channels according to the “each to each” principle;

The telephone territory has several numbering zones. One or more automatic telephone exchanges are installed in the zone;

Each telephone exchange for outgoing and incoming communications must rely on two AACs, on the AAC of its territory and the AAC of the adjacent territory;

The long-distance telephone network is built with bypasses, i.e. with the organization of direct paths between automatic telephone exchanges based on high-utilization channel bundles (HU) and with the dumping of excess load on bypass paths - intermediate (IP) and last choice (PPV) to the UAC;

The long-distance telephone network is built on a hierarchical principle and has two levels of hierarchy - AMTS-UAK (OTS).

The long-distance network is calculated for normal network operating conditions, and each pair of telephone exchanges has an optimal (cheapest) PPV, which passes through its own ACN (OTS), or inter-adjacent one. All PPV sections must contain high-quality service channel bundles, calculated with a loss probability of 0.01. [ 10 ]

Organization of long-distance communication using satellite channels is possible on direct bundles between automatic telephone exchanges, as well as on OPP bundles to foreign UACs. In this case, the channel requires the transmission of information about the presence of a satellite channel in the connection. The connection should not have more than one section using satellite channels.

For long-distance and international connections, when the distance between telephone exchanges exceeds 8000 km, to ensure the specified transmission quality, it is necessary to turn on equipment for echo suppression.

The number of switching sections for long-distance connections is no more than 5. The capacity of the telephone network should be increased by installing digital switching equipment and laying channels (lines) with digital transmission systems.

Based on operating digital PSTN equipment (mainly long-distance networks) and newly installed digital switching equipment and transmission systems

a public digital communication network (PSN OP) should be formed. Subscribers of this network should be provided with an end-to-end digital path from subscriber to subscriber or from hub (PBX) to hub (PBX) and ISDN (ISDN) and intelligent network services will be provided. At the initial stage, this opportunity is provided to a limited number of consumers in a limited number of directions, with subsequent expansion of both subscriber and network capacity.

In parallel with increasing the capacity of the long-distance telephone network, equipment on local telephone networks that has exhausted its service life must be replaced with digital equipment.

All digital local networks should be included in electronic telephone exchanges via digital transmission systems, thus creating elements of a future public digital network.

1. Principles of building an intrazonal telephone network

The intrazonal telephone network is a set of automatic long-distance telephone exchanges (ATS), simultaneously included in the intercity network, custom trunk lines (CLL) and trunk lines (CLM) connecting local networks with ATE, trunk lines between different local networks in the zone, if available electronic telephone exchanges, as well as channels between telephone exchanges, if there are several telephone exchanges in the area.

One or more telephone exchanges can be installed on the intrazonal network.

The organization of an intrazonal network with one telephone exchange in a zone is built according to the radial principle, i.e. each local network is included in the automatic telephone exchange for outgoing communication via ZSL and incoming communication via SLM. When installing program-controlled stations on local networks, it is possible to organize direct paths between different local area networks if there is gravity between them.

If there are several telephone exchanges in a zone, the intra-zone network can be built with bypasses, and various options for constructing the network are possible. [ eleven ]

When placing several telephone exchanges in different cities of the zone, it is recommended to build a network in which local networks are divided by telephone exchange, i.e. each local network is connected by high-quality service LSL and SLM bundles to the core PBX. These local networks can be connected with other ATEs if there is sufficient gravity and the technical capabilities of ATEs with high-use SLM beams. All ATEs of the zone must communicate with each other on the principle of “each to each” with bundles of channels of high quality of service.

When placing several ATEs of a zone in one city, it is recommended to build an intra-zonal network, in which all local networks should be connected to one ATE by high-quality SLM bundles, and with other ATEs in the city, the local network can either be connected by SLM bundles of high quality service, or by SLM bundles of high quality. use, or have no connection.

Each local network is connected by LAN bundles, as a rule, into one ATE.

All the city's automatic telephone exchanges must be interconnected by high-quality service channel bundles. Options for organizing intrazonal communication are presented in Fig. 6 and 7. The organization of semi-automatic communication from the DC and the cities of the zone is carried out through the telephone operator of the telephone office. If there is an electronic system in the automatic telephone exchange area, this communication is organized via a bundle of closed-circuit lines, while display workstations are installed at the call centers. It is allowed to organize semi-automatic communication via direct channels from the DC switch to a coordinate-type automatic telephone exchange.

On intrazonal networks, satellite systems can be used, along with cable, radio relay and fiber-optic transmission lines. Satellite channels can be used on direct beams between local networks, as well as when communicating with automatic telephone exchanges for intra-area communications. When using a satellite channel, echo cancellation equipment must be turned on.

1. Principles of building city telephone networks

City telephone networks should be built using predominantly digital electronic (digital) switching equipment and linear paths of digital PCM transmission systems. Decadal-step automatic telephone exchanges and units must be decommissioned and dismantled before 2005. Replacement of coordinated automatic telephone exchanges is carried out as the equipment wears out.

Subscriber terminal devices must be included in the switching equipment of the city network in the following ways:

Directly to the PBX using two-wire subscriber lines (AL);

Directly to the automatic telephone exchange using ALs equipped with transmission systems, subject to ensuring the operation of telefaxes and the installation of data transmission (TD);

Over digital subscriber lines using multiplexing equipment and digital transmission systems;

In substations (SS) included in the automatic telephone exchange;

In institutional and industrial telephone exchanges (UPTS).

On newly introduced PBXs, paired activation of telephone sets is not allowed. The main connection method should be to connect the terminals directly to the PBX via two-wire subscriber lines.

Communication between GTS stations among themselves, as well as with automatic telephone exchanges, is currently carried out via one-way trunk lines. With the introduction of OCS on the GTS, it is recommended to use two-way trunk lines between digital stations.

According to their structural characteristics, hydraulic structures are classified as follows:

Not zoned;

Zoned without knotting;

Regionalized with incoming message nodes (IMS);

Regionalized with nodes of outgoing and incoming messages (with UIS and UVS).

A non-zoned telephone exchange has one telephone exchange, into which subscriber terminal devices are connected directly or through a public telephone exchange and substations. On an analogue telephone network, such a structure is economically feasible with a network capacity of up to 8 thousand numbers. On a digital GTS, in conditions of widespread use of substations, a non-zoned structure can be economically feasible with a network capacity of several tens of thousands of numbers.

Regionalized telephone exchanges without node formation have several regional telephone exchanges, which on an analog network communicate with each other using a fully connected circuit, and on a digital network - according to a fully connected circuit with bypass directions.

A zoned structure on an analogue GTS is economically feasible with a network capacity of up to 80 thousand numbers, and on a digital network - up to several hundred thousand numbers.

Regionalized GTS with nodes for incoming messages are divided into hub areas, in each of which, in order to concentrate the load on the ATS of the hub area, air traffic control systems are installed. Communication between PBXs of different areas, as a rule, is carried out according to the PBX-UVS-PBX scheme through the switching equipment of the incoming message center located in the hub area in which the incoming PBX is located. All telephone exchanges in the hub area have a common one hundred thousand (two hundred thousand) index. Analogue regionalized telephone networks with airborne communication systems can have a capacity of up to 800 thousand numbers, and digital telephone networks - up to several million numbers.[ 12 ]

The switching equipment of the UIS is located near the telephone exchanges from which the outgoing telephone load is concentrated. One UIS can serve the automatic telephone exchange of one or several hub areas. As a rule, communication from a given group of stations to stations of one million zone passes through each UIS.

The switching equipment of the UVS is located in the hub area, for whose automatic telephone exchange the UVS combines the incoming load. Regional automatic telephone exchanges located within one hub area are connected according to the same schemes as on a gas telephone exchange with a hydrocarbon station. For analogue stations, the maximum number capacity of an automatic telephone exchange (at the end of the development stage) should, as a rule, be a multiple of 10 thousand numbers, and the actual number capacity of a hub area should be 100 thousand numbers.

The above principles for constructing GTS are implemented in analog GTS and will not be modified during communication between analogue PBXs for the entire remaining life of these PBXs. The introduction of digital PBXs should be carried out using the PBX “overlay network” method. Basic rules for creating an "overlay network":

All communications between digital PBXs must be carried out only through digital PBXs and nodes;

When communicating between digital automatic telephone exchanges, linear paths of digital transmission systems must be used that meet the CCITT G series recommendations when coordinating interfaces;

Within one local network, for any connections, as a rule, only one transition is allowed between the “overlay” and existing networks;

Newly introduced digital PBXs should only be included in the “overlay network”;

Communication between digital and analogue telephone exchanges must be carried out via linear paths of digital transmission systems that meet the CCITT G series recommendations with the installation of analog-to-digital conversion equipment and coordination of signaling systems on the side of analogue telephone exchanges;

Digital stations and nodes can be located on the same territory of the urban telephone system or even in the same buildings with analogue telephone exchanges and nodes.

The implementation of digital switching and transmission systems on an analog network should not require the installation of special interface devices at existing stations and nodes, except for equipment that includes analog-to-digital conversion (ADC) devices and signaling system coordination devices. However, modifications to existing equipment are not permitted.

All interface functions must be provided in the systems being implemented.

The structure of existing and under construction overlay networks of digital stations, as a rule, corresponds to the principles of constructing a GTS.

The network of lines connecting subscribers with switching nodes (subscriber network) is built mainly using a cabinet system. In this case, ALs are divided into:

Trunk (from the automatic telephone exchange to the distribution cabinet RSh);

Distribution (from distribution cabinet RSH to distribution box RK);

Subscriber wiring (from the junction box to the subscriber's device).

Thus, the cables laid in the corresponding section of the network are called connecting, trunk, distribution and subscriber cables. A promising direction is the creation of digital subscriber access networks. The first element of the telecommunications system is a set of terminal and other equipment that is installed at the subscriber’s (user’s) premises. In English technical literature, this element corresponds to the term Customer Premises Equipment (CPE). The second element of the telecommunications system is the subscriber access network. Its role is to ensure interaction between equipment installed at the subscriber's premises and the transit network. Typically, a switching station is installed at the interface between the subscriber access network and the transit network. The space covered by the subscriber access network lies between the equipment located on the subscriber's premises and this switching station. In a number of works, the subscriber access network is divided into two sections:

Subscriber lines AL (Loop Network), which are considered as individual means of connecting terminal equipment;

Transfer Network, which serves to improve the efficiency of subscriber access facilities. This fragment of the access network is implemented on the basis of transmission systems; in some cases, load concentration devices are also used.

The third element of the telecommunications system is the Transport Network. Its functions are to establish connections between terminals included in various subscriber access networks, or between a terminal and means of supporting any services. The transit network can cover an area either within the same city or village, or between the subscriber access networks of two different countries.

The fourth element of the telecommunications system provides the means of access to various telecommunication services (Service Nodes): the nodes that support the services. An example of such nodes can be the workplaces of telephone operators and servers in which information is stored.

Thus, the access network in general terms can include both subscriber sections and connecting lines between automatic telephone exchanges. [ 13 ]

1. Principles of constructing rural telephone networks

On the STS, radial (single-stage scheme) and radial-nodal (one- and two-stage scheme) network construction should be used with the possibility of using direct and bypass paths.

Based on their purpose and location on the network, STS telephone exchanges are divided into the following types:

CS located in the regional center, performing simultaneously the functions of the regional center's telephone exchange and the STS transit hub. The CS includes connecting lines (CL) of node stations (US) (with a two-stage construction scheme) and CL of terminal stations (OS) (with a single-stage construction scheme). Through the CA, communication is carried out with the special services, the MTS of the regional center and with the automatic telephone exchange;

SS located in any settlements of the rural area. CS provide a subscriber network and are terminal-transit stations, which include trunk lines from the central station, OS and other CS. Through the CS, transit communication is carried out between the OS included in it, as well as between these OS and the CA or other CS (when using direct paths at the CS level);

OS located in any settlements of the rural area.

OS trunk lines (depending on the network design) are included in the CA or CS, as well as in other OS or CS (when using direct paths between the OS or between the OS and other CS).

The choice of STS construction scheme (single-stage or two-stage) is made during design based on a technical and economic comparison of STS construction options. Nodal and central stations STS must provide four-wire transit of the spoken path. All rural telephone exchanges must be equipped with equipment for automatically determining the category and telephone number of the calling subscriber (Caller ID). Communication between STS stations can be carried out via one-way, two-way, separate or common (universal) trunk lines for local and long-distance communications, and communication between the central station and city automatic telephone exchanges (MTS) and automatic telephone exchanges can be carried out via one-way connecting lines. Connecting lines of analog stations of STS are organized, as a rule, on the basis of voice frequency (VF) channels. During a feasibility study and compliance with established standards for attenuation of the spoken path, physical circuits can be used to organize trunk lines.

The creation of an overlay digital network on the STS begins with the installation of a new digital digital network; the analog digital network is transferred to the rank of a node network. All existing analogue stations, as well as digital ones connected to the former CA via analogue paths, remain included in it. All digital stations connected to the former CA via standard PCM paths switch to the new digital CA. When introducing a new digital CA, existing CAs are transferred to the rank of OS, and to ensure communication between the OSs previously included in them and the former CA, a network node is also organized on the former CA.

All subsequent development of the district's STS based on digital communication systems (ATS, transmission systems), included on a radial basis into the district's digital digital network, is carried out within the framework of an "overlaid" digital network. The inclusion of a digital DS in a digital zone automatic telephone exchange should occur only through digital channels of digital transmission systems. If a digital CA is included in an analogue PBX, it can be connected via analog channels.

At analogue STS stations the following may be included:

Individual two-wire subscriber lines (AL);

Subscriber lines included in the equipment of transmission systems;

Concentrators;

Radiotelephone communication lines, radio extenders;

Local outgoing payphones;

Payphones for local outgoing and incoming calls;

Long-distance outgoing payphones;

Negotiation points for conducting outgoing and incoming long-distance negotiations.

STS digital stations must include:

Individual analog two-wire AL directly to the telephone exchange or through substations and multiplexers;

Digital AL (for PBX with ISDN functions]

Radiotelephone communication lines;

Payphones for local outgoing calls, local outgoing and incoming calls, long-distance outgoing calls;

Negotiation points for conducting outgoing and incoming long-distance negotiations.

A specific problem of STS is the inclusion of small settlements and individual houses spread over long distances. One of the ways to solve this problem is to include several low-capacity automatic telephone exchanges in one or two PCM paths in series. To install telephones in remote, sparsely populated and hard-to-reach rural subscriber points, it is recommended to use AL over transmission systems, telephone concentrators, low-channel radiotelephone communication systems and radio extenders, and low-channel radio relay equipment.

If there are dispersed groups of subscribers, a ring distribution digital transmission system (DSTS) can be used, which ensures the allocation of channels at intermediate points through blocks connecting subscriber terminals to the automatic telephone exchange.

The choice of a set of options for constructing a subscriber network should be determined during its specific design.

1. Construction of a wired broadcast network

A wired broadcasting (WB) network is a complex of structures and devices designed to receive signals from audio broadcasting programs, amplify their power, distribute them via a wired network and deliver them to a wide range of listeners. PV networks consist of station and linear structures.

Station structures are a complex of various devices: power amplifiers, control, monitoring and switching equipment. Linear structures of the PV network or radio broadcast networks (RTS) are a set of various feeder and subscriber lines, house wiring, transformers and other linear devices that serve to transmit broadcast programs from amplifiers to sockets installed at subscribers. The delivery of sound broadcasting programs to the radio broadcasting unit is carried out via radio or wire channels.

The PV network is built on an administrative-territorial basis: locality, rural area.

The organizational and technical unit of the network is the radio broadcasting node RTU, or the PV node. The RTU includes station and linear structures, as well as subscriber devices. Station structures are used to receive, amplify and distribute audio broadcast programs along the lines and control automated PV units. Linear structures are elements of the path connecting the amplifier to the subscriber installation. The complex of linear structures of the RTU is called the distribution network (PC). A construction system in which audio broadcasting programs are supplied from one station is called an RTU network with centralized load power supply. A construction system in which programs are supplied from a central wire broadcasting station (CSPB) to several reference amplification stations (RAS) and are then distributed over the subscriber network is called an RTU network with decentralized power. [ 14 ]

In rural areas, a system with a centralized supply of broadcast programs is mainly used.

The distribution network circuits are divided into subscriber and feeder circuits. The subscriber circuit (AC) powers subscriber devices. It also includes in-house distribution wiring. Feeder circuits are divided into distribution and main circuits. The distribution feeder (DF) feeds the subscriber circuits, the main feeder (MF) - the distribution feeder circuit. On a rural PV network, it is allowed to connect the AC directly to the MF.

Wired broadcasting networks are divided into single-link, two-link and three-link. Single-link - a network consisting of ACs connected directly to the RTU station is used in small settlements served by low-power nodes. In a two-link network, subscriber circuits (link I) are connected to distribution feeders (link II). Two-link networks are used in large rural settlements, as well as for connecting distribution networks of nearby settlements to the RTU. A three-link network consists of a main feeder connected to the RTU station (link III), distribution feeders (link II) fed by the main feeder, and an AC. It is advisable to organize a three-link network in the case of connecting large settlements to the station. This network construction is used to organize wired broadcasting in individual agricultural productions when servicing two or three farms with one node.

One of the elements of a wired broadcasting network is linear transformers, which convert the voltage of the linear path. They are divided into subscriber and feeder. The subscriber transformer is used to match the low input impedance of the AC with the high resistance of the feeder (RF or MF), or the output of the amplifier and lower the voltage to the required value.

Feeder transformers are designed to match the initial resistance of the amplifier with the input resistance of the circuits connected to it and match the joints of feeders with different input resistances, as well as lower or increase the voltage to the required value.

Depending on the functions performed, FTs are divided into:

Main feeder step-up transformer (TMF), installed between the amplifier output and the MF input to increase the voltage, match the output impedance of the amplifier with the input impedance of the MF and eliminate galvanic coupling between the wires of the circuits connected to the output of one amplifier;

Step-down transformer of the main feeder (TPMF), installed at the end of the MF to reduce the voltage and connect the RF. A set of a step-down transformer, protective, switching and instrumentation devices, automation and backup power supply devices is called a transformer substation (TS) and is used on a city wired broadcasting network. On a rural network, a simplified transformer substation (UTS) is used, consisting of a step-down transformer, protection devices and non-operational switching;

Distribution feeder transformer (DFT), installed between the output of the amplifier (or MF) and the input of the electrically long RF to increase or decrease the voltage, eliminating the galvanic connection between the wires electrically long chains, connected to the output of one amplifier (or the output of the MF), and matching the resistance of the connected electrical circuits;

Matching transformer (MT), installed at the junctions of circuits of dissimilar structures and materials - to match their resistances;

A separating transformer (TP), installed on a feeder suspended on supports together with STS circuits, for galvanic separation of the joint suspension section from other sections or on wire broadcast circuits in areas exposed to the dangerous influence of high-voltage lines, as well as to reduce the level of induced dangerous voltages;

Correction transformer (TC), installed on electrically long RFs to equalize the frequency response of the linear path;

Tap transformer (TO), installed between the feeder and the tap from it to match their resistances, as well as to coordinate the joints of dissimilar structures of the feeder and tap circuits.

Audio broadcasting networks in cities and rural areas have a three-program wire broadcasting (TPB) system. The basis for rural multi-program wire broadcasting is the TPV system used in cities. It is planned to preserve the first main low-frequency program according to the existing system for organizing the PV network. The second and third programs are transmitted using frequency division transmission systems equipment with two sidebands and 78 and 120 kHz carriers.[ 15 ]

The TPV network construction system provides for the installation of two transmitters in the RTU. Using transmitter connection devices, amplitude-modulated high-frequency signals are transmitted to main or distribution feeder lines. The transformer substation is equipped with a transformer substation connection device. Bypass devices for subscriber transformers are installed on distribution feeders. To ensure a consistent operating mode of high-frequency audio broadcasting channels on the network, it is necessary to install matching devices on cable inserts, autotransformers of taps at the input of feeder taps, matching loads connected at the end of the RF and taps. Individual three-program receivers are mainly used as receiving devices, and in some cases group receivers are used for public buildings.

The transmitting device of the rural hot water supply system is made of transistors. It is controlled by devices coordinated with the equipment of the automated single-program broadcasting unit. The operation of the transmitting device is controlled by monitoring and backup control equipment (ACRU).

Conclusion

To summarize this course work, I would like to note the prospects for the further development of telephone communications in Russia.

Over the past ten years, the telecommunications industry in Russia has undergone very large transformations associated with the transition of the entire economy to market relations. As a result of privatization, the state monopoly on the development of the industry and management of enterprises was destroyed. The state has ceased to be the main source of financing for the industry. At the same time, it retained a number of important regulatory functions, such as licensing, control over the level of tariffs on local telephone lines, and a controlling stake in the Svyazinvest holding, which, in turn, controls seven united regional communications companies. Market forces began to play a significant role in the development of the industry. This is especially typical for completely new areas of telecommunications business that have emerged in recent years, in particular such as mobile communications and data transmission. A number of new telecommunications enterprises have emerged, including those created in the form of alliances with foreign partners. During these years, international cooperation was one of the main factors contributing to the technological development and modernization of the telecommunications industry in Russia. It provided Russian enterprises in the new economic conditions with additional direct investments and trade loans for the purchase of modern equipment.

At the moment, we can talk about an insufficient flow of investment into the telecommunications industry in Russia. Along with the need to improve the investment climate in the telecommunications market, the type of regulatory agency has a fundamentally important impact on the market. Only the presence of an independent regulatory agency allows not only to significantly reduce prices, but also to significantly increase the range of services offered. There is no such agency in Russia. All regulatory structures are tightly linked to government agencies. This does not exclude the adoption of a regulatory decision that has a political overtone, which allows to increase the prestige of the authorities, but does not meet the interests of the market and the welfare of society. In this case, one should not confuse (or replace) the coordinating actions of the state (for example, preventing operators from abusing the right to set prices for services provided, protecting the national producer, etc.) and the desire to influence the market using administrative resources (make regulatory decisions, allowing certain groups to have advantages in the market, to lobby the interests of “their” producers, etc.).

Summarizing all of the above, it can be noted that, despite the dynamic development of the national telecommunications industry as a whole, which has one of the highest rates of development among telecommunications markets in the world, the domestic telecommunications market has the following features:

different market segments are developing unevenly;

the volume of investments is insufficient to conduct full-scale telecommunications activities;

regulators are an integral part of government and have a strong protectionist bent;

there is no scientifically based long-term federal program creation, development and improvement of the national telecommunications infrastructure.

The sector of the telecommunications market, which includes telephone communications, belongs to the group of dynamically developing, capital-intensive, socially significant sectors that bring the lion's share (about 80%) of the profits of the entire industry. In terms of the number of users, telephone communications are currently second only to the television and radio broadcasting segment. Total revenues in the Russian telephone sector are projected to more than triple by 2011.

The creation of a Russian information and telecommunications infrastructure should be considered as the most important factor in the rise of the national economy, the growth of business and intellectual activity of society, and the strengthening of the country’s authority in the international community. [ 16 ]

List of used literature

1. Constitution of the Russian Federation: adopted by all. by vote 12 Dec. 1993 - M.: Legal. lit., 2000. - 61 p.

2. Civil Code of the Russian Federation. Part one of November 30, 1994 N 51-FZ (as amended on November 4, 2007) // SZ RF. - 1994. - No. 32. - Art. 3301.

3. About communication: Feder. Ross's law Federation dated July 7, 2003 N 126-FZ

5. To help radio amateurs: electronic components / A. P. Kashkarov. - 2004. - N 4-5. - P. 82 - 89.

6. GOST 19472-88 “National automated telephone communication system. Terms and Definitions".

7. History of the opening of the first communication line St. Petersburg - Moscow in documents // Electrosvyaz. – 1998. – No. 10– 25 p.

8. Switching in communication systems and networks /A. N. Berlin. - M., 2001.- 444 p.

10. Fundamentals of radio electronics and communications: Textbook. manual for universities / V. I. Kaganov, V. K. Bityugov.

11. Experiments in studying the propagation of alternating current along long wires. Application to long-distance telephony // Voitsekhovsky P.D.// PTZh. – 1896, May, p. 709-726; June, p. 847-854

12. Domestic telecommunication systems: Textbook. manual for universities / Yu. K. Sharipov, V. K. Koblyakov.

13. From plasma TV to the mini-disc: Expertise // "Izvestia" No. 215, 1997.

14. Development of the Russian telecommunications industry, Korneev I., published in the magazine "CIO" No. 1 dated January 28, 2005

15. Russian State Historical Archive - RGIA, f. 1289, op. 2, d. 1618, l. 233.

16. Telegraph devices: [From the collection of Polytechnic. museum: Catalog] / S.V. Delibash, G.A. Galustyan, L.V. Gurskaya; Scientific ed. G.G. Grigoryan.

1 Russian State Historical Archive - RGIA, f. 1289, op. 2, d. 1618, l. 233.

JSC telecommunications impossible without assessing the level achieved development telecommunications in the region, ... TP is an integral indicator development telecommunications, reflecting the state networks in general, and in the absence of data...

Before its invention in the 19th century. communication systems and mechanisms, the communication process itself was very difficult and slow. People sent letters to each other with messengers or transmitted signals using drums, smoke, fires, church bells, mirrors These methods were good only for communication over short distances; messages took a very long time to reach distant points. Even after the advent of steamships, it took several months to deliver a letter, for example, from Europe to Australia.

The Frenchman Claude Chappe (1763 - 1805) invented a communication system called telegraph, which means “writing from afar.” It worked like this. Special towers were built on the tops of the hills. Each tower had a special design with two long slats that could take 49 positions. Each position corresponded to a letter or number. Operators transmitted messages from one tower to another. This system worked very successfully. TO mid-19th V. the length of its lines in France alone was about 4828 km.

First electric telegraph created in 1837 by English inventors William Cook (1806-1879) and Charles Wheatstone (1802-1875). Electrical signals were sent through wires to a receiver. They operated arrows that pointed to different letters. This is how the message was conveyed.

In 1843 American artist Samuel Morse (1791 - 1872) invented a new telegraph code that replaced the Cook and Wheatstone code. He developed signs for each letter consisting of dots and dashes. When transmitting a message, long signals corresponded to dashes, short signals to dots. Morse staged a demonstration of his code by laying a 6 km telegraph wire from Baltimore to Washington and transmitting news of the presidential election over it. Morse code is still used today.

In 1858, Charles Wheatstone created a system in which an operator, using Morse code, typed messages onto a long strip of paper that fed into a telegraph machine. At the other end of the line, the recorder was typing the received message onto another paper tape.

Subsequently, the recorder was replaced by a signaling device that converted dots and dashes into long and short sounds. The operators listened to them and recorded the text of the message.

Today it is impossible to imagine life without a telephone. It is used everywhere and people's lives largely depend on this device. It's hard to believe that the phone was released just before the turn of the century. The official date of its invention is usually considered to be 1876. Naturally, as in the cases of other technical inventions, research and experimentation related to the telephone began much earlier.

Interestingly, the telephone was actually invented simultaneously by two researchers - Bell and Gray - independently of each other. Alexander Graham Bell, who is generally credited with inventing the telephone, was more fortunate, beating Gray to a patent application, which he received on March 7, 1876.

They say that when in 1876 Chief Engineer British Posts and Telegraphs Sir William Preece heard about the invention of the telephone, he exclaimed: “Perhaps the Americans need a telephone, but fortunately we still have enough messengers!” This exclamation turned out to be too hasty. No invention in the world has been recognized so quickly and has not developed as rapidly as the telephone.

Like many important inventions In history, the phone appeared by mistake. It arose as a result of attempts to develop a device for transmitting several Morse code signals over one wire. Today this method is known as signal multiplexing or multiplexing. Legend has it that Bell experimented with a multi-channel telegraph transmitter while his assistant Thomas Watson watched the receiver in another room. After accidentally spilling acid on his trousers, Bell called out to his assistant: “Mr. Watson, help me quickly!” In the heat of the event, he forgot that Watson could not hear him. But, to his great surprise, Watson appeared very quickly: he heard Bell call from the receiver. History is silent about how Gray came across the idea of ​​the telephone, but the basic principles of his invention are very reminiscent of Bell’s principles. There is no need to trace in detail the minor differences between the Bell and Gray telephones. One thing is clear: the telephone has become an invention whose time has come. The first phone Bell made by accident didn't work well, but it worked, and that was great. In its original form, the Bell telephone was not suitable for widespread use. But the prospect of this invention, which could send sound messages through wires, was obvious, so soon began active work to improve the phone. As early as 1878, the first commercial telephone exchange was built in New Haven, Connecticut.

The telephone satisfied a very specific social need, making it possible to communicate over long distances without the use of intermediate codes and bulky telegraph apparatus. Communicating on the phone was simple, familiar and convenient. That is why the phone very quickly gained wide recognition throughout the world and its implementation and development became big business.

Especially for this new and important branch of the communications industry, one of the largest corporations of the twentieth century was created - the American Telegraph and Telephone Company (AT&T - American Telegraph and Telephone Company). It was incorporated as a legal entity in March 1885 and soon came to control virtually the entire rapidly growing telephone network throughout the United States. From the very beginning of its activity, AT&T was in extremely favorable conditions as a legal government monopoly.

Because of the corporation's immense size, it had the luxury of large research laboratories. AT&T remained at the forefront of technology simply because no one else had the means to carry out the necessary developments at the level of Bell Laboratories, AT&T's research division.

In Russia, in St. Petersburg, they began to use telephones more than a hundred years ago, in 1882. Then the first telephone exchange for 128 subscribers opened in the capital. A year later, there were already 604 telephone sets in St. Petersburg, in 1890 - 1829, and after another five years - 2858 telephone sets, and their number was rapidly increasing.

Soon telephone lines connected St. Petersburg with Gatchina, then with Peterhof and Tsarskoe Selo. Moscow and other Russian cities were telephoned. But more than a decade and a half passed before telephone wires were laid between St. Petersburg and Moscow, i.e., the first long-distance telephone line in Russia was opened.

That's what it is an important event happened very late, technology is least to blame. Five years after the installation of the first telephone in the capital, the Main Directorate of Posts and Telegraphs received a request from entrepreneurs A.S. Stolpovsky and F.P. Popov to grant them the rights to establish direct telephone communication between St. Petersburg and Moscow. “In view of the undoubted importance that telephones have, and the enormous public and state benefits they bring, the thought of a telephone connection is very timely major centers state and industrial life."

However, these seemingly convincing arguments did not make the proper impression on the leaders of the postal and telegraph department, and the proposal of Stolpovsky and Popov was decisively rejected “due to many ambiguities.” It took two long years to come to the conclusion that establishing a telephone connection between the two cities was advisable and that such a connection “should provide significant benefits in a very short time.” But only 5 years later, in 1898, Moscow and St. Petersburg were connected by a telephone line.

At the same time, human thought did not stand still. The experiments of Michael Faraday and his compatriot and follower Clark Maxwell led scientists to the conclusion that an alternating magnetic field generated by a continuously changing current creates an electric field in the surrounding space, which in turn excites a magnetic field, a magnetic field excites an electric field, etc. Interrelated , the magnetic and electric fields created by each other form a single alternating electromagnetic field, which continuously, as if separating and moving away from the place of its excitation, spreads throughout the surrounding space at the speed of light (300,000 km/s). The phenomenon of excitation of electromagnetic fields by alternating current began to be called radiation electromagnetic vibrations, or radiation of electromagnetic waves. Meeting conductors on their way, the magnetic components of electromagnetic oscillations excite an alternating electric field in these conductors, creating alternating current, similar to the current that excited electromagnetic waves, only incomparably weaker. This remarkable phenomenon was the basis for the technology of radio transmission and radio reception. So, in 1888, the German scientist Heinrich Hertz managed to experimentally prove the very fact of the existence of electromagnetic waves and find the possibility of their detection. Hertz's experiments could not help but lead to the idea of ​​transmitting messages using electromagnetic waves, that is, communicating without wires. Let us cite a statement on this matter from only one scientist, the Englishman W. Crookes. In his remarkable article “Some Possibilities of Using Electricity” (1892), he wrote: “... electrical vibrations with a wavelength of one yard or more easily penetrate through all sorts of media (walls, fog) that are transparent to them. Here the amazing possibilities of telegraphy without wires are revealed.” He further writes that the research being carried out in this area could any day lead to practical results. He describes in detail the principles of wireless telegraphy, points out the need to use waves of different lengths, tune the radio transmitter and radio receiver to the selected wave, talks about the use of directional antennas, Morse code and a number of other elements of the system for transmitting and receiving radio waves, which later began to be used in radio communications.

Conducting experiments with Hertz waves, the English scientist O. Lodge (1851-1940) came closest to creating a radio communication system. But he was engaged in “pure science,” creating instruments to demonstrate Hertz’s experiments, and did not set himself practical tasks. Lodge himself wrote in 1923: “... I had no sense of perspective and understanding of the exceptional significance that these experiments had for the fleet, trade and, of course, for reliable communications in peacetime and war.”

The first sufficiently sensitive and reliable receiving device, without which radio communication is unthinkable, was created by our compatriot, a talented physicist, at that time already a prominent specialist in the field of electrical engineering, teacher of the Mine Officer Class in Kronstadt, Alexander Stepanovich Popov. While conducting experiments with Hertz's rays, A. S. Popov, relying on the work of O. Lodge, in April 1895 made a coherer receiver with relay amplification and automatic synchronous decohering using a bell hammer, which sounded the reception of radio wave parcels (signals). Alexander Stepanovich demonstrated his receiver, which received radio waves emitted by a Hertz vibrator, at a meeting of the Russian Physicochemical Society (RFCS) on May 7 (April 25, O.S.), 1895, delivering a report “On the relationship of metal powders to electrical vibrations.” The signals were received by a piece of wire connected to the device. As soon as the vibrator began to emit electromagnetic energy, the receiving device responded to it with a trill of a bell. This device was the world's first radio receiver, and the piece of wire attached to it was the world's first antenna.

In the same 1895, when A.S. Popov created his own receiver, the young Italian Guglielmo Marconi conducted experiments with electromagnetic waves, the purpose of which was to create a device for transmitting messages. These experiments are known only from the memoirs of contemporaries; there were no publications on this subject at that time. The following year, on June 2, 1896, he submits an application in Great Britain for “improvements in the transmission of electrical impulses and signals and in apparatus for the same.” The patent was issued on July 2, 1897, and only after that a detailed description of the device proposed by G. Markonk appeared. It turned out to be very similar to A.S.’s device. Popova.

In 1896, the world's first radiogram was transmitted and received, recorded on a telegraph tape. In the spring of 1897, radio signals were transmitted from the ship to the shore over a distance of 640 m. And two years later, in 1899, after the discovery of the possibility of receiving radio signals using telephone handsets by ear, the radio communication range had already reached 35 km.

But that was only the beginning. The progress of radio electronics and, in particular, radio communications cannot fail to impress. Over the first quarter of a century, it has gone from imperfect spark systems for transmitting and receiving damped oscillations to tube receivers and generators, to high-quality antenna systems. In the formative years of radio communications, it was believed that in order to increase the range, it was necessary, along with increasing the transmitter power, to increase the wavelength, which led to the use of radio waves hundreds and thousands of meters long (medium waves - SW and long waves- DV) and transmitters with a power of tens and hundreds of kilowatts. In the early 20s of our century, the sensational property of short waves (KB) was discovered. With low transmitter powers, they could, due to reflection from the ionized layers of the atmosphere, overcome huge distances. The “victorious march” of KB began, on which long-distance radio broadcasting and radio communications operated for six to seven decades. The development of new ranges, including the ultrashort wave (VHF) range, was a completely natural process in the development of science and technology and corresponded to the practical need to expand the range of frequencies used.

The number of transmitting means was growing rapidly; for their operation without mutual interference, new frequencies were required, as well as international regulation of their use. In addition, the usual ranges of DV, SV, KB turned out to be completely unsuitable for a number of new services, for example, high-quality electronic television, radar, which occupy a wide frequency band, measured in megahertz. In the early 30s, the problem of detecting aircraft using radio waves became urgent, the solution of which marked the beginning of radar, which largely contributed to the formation and rapid improvement of new technologies in microwave radio electronics.

Let us turn to modern radio communications in the broad sense of this concept as an industry electrical communication, which has become one of the most important infrastructures in technically developed countries. The intensive process of integration of various types of telecommunications makes it possible today to consider it as a single complex of means of transmission, reception, information processing and computer technology, one of the main areas of improvement of which has become digital signal processing. In Russia, which is a little behind in this area, work on the creation and implementation of digital communications and telecommunications is gaining momentum. For the first time, modern high-speed digital radio relay lines with a capacity of each set of communication channels of 140 Mbit/s were built, and construction of a digital radio relay highway with a length of more than 8,000 km of similar capacity is underway. These lines are part of an international fiber optic digital communications ring that encircles Earth. The Russian section of this ring will become the basis for the creation of regional digital communication networks, including using digital radio relay lines of lower capacity, and these networks will merge into the main highway.

TO priority areas The development of telecommunications also includes mobile radio communication systems. For many years, the main type of such communication we had was the Altai radial-zonal radiotelephone system. And only in the last few years has the introduction of very advanced cellular systems begun, which have gained great popularity in technically developed countries.

V. O. Shvartsman

The development of telecommunications began more than 160 years ago - with the advent of telegraph communications. Now there are 11 types of telecommunications.

As can be seen from the table, the vast majority of types of telecommunications (10 out of 11) are intended for humans - both the sender and the recipient of information. Only data transfer is used to exchange information between computers and between a person and a computer.

When considering the table, a number of questions arise:

4. Is it possible to provide services beyond the scope of direct communication between people using telecommunications?

To answer these questions, we will use the results indicating the information capabilities of some types of telecommunications.

It is well known that the advent of telecommunications made it possible for a person to transmit various information over much greater distances than through direct communication. But besides this, communication means have various information capabilities (see table).

Now let's try to answer the questions posed above.

1. Why did the development of telecommunications begin with telegraphy?

Apparently, there are several reasons for this.

1. Pattern of development. As a type of electrical communication, telegraphy had a long history - from optical and sound telegraphs (signaling with fires and semaphore, drumming, etc.) to electrochemical and elementary electromagnetic.

2. Historical conditioning. Since the development of technology is determined by the state of the relevant areas of science and practice, in the first third of the last century the prerequisites appeared for the creation of an electromagnetic telegraph.

3. Technical capabilities. The easiest way to send messages over a distance is to use electricity by turning it on and off during transmission, as well as the attraction of the magnetic needle by an electromagnet turned on during reception.

2. What is the driving force behind the emergence of new types of telecommunications?

As follows from the table, with the advent of new types of telecommunications, the volume of information obtained with their help is approaching the volume of information obtained through direct communication between people. Therefore, as soon as opportunities arose for converting sound vibrations created by human speech into electrical signals and converting them back at reception, telephony arose (about 40 years after telegraphy), which sharply increased the volume of transmitted information compared to direct communication (from 7 to 45 %).

After this, fax communication was organized, which significantly expanded a person’s capabilities in transmitting not only text and audio messages, but also drawings, drawings, and photographs.

The emergence of this type of communication became possible after the implementation of the idea of ​​sequential transmission of images across elements and the development of methods and devices capable of converting still images into electrical signals.

Photocells were used as transmitting converters, and at receiving – electric light (with recording on photographic paper), electrochemical (with recording on paper coated with a special composition that reacts to the strength of the current), electrostatic (with recording on a special paper that reacts to the magnitude of the electric charge) and other methods. However, more than half of the information (see table) received by a person using the organs of vision could not be transmitted using communications until the problems of converting moving images into electrical signals and vice versa were solved. So, as a result of the invention of cathode ray tubes - the iconoscope (transmitting) and the kinescope (receiving) - television appeared.

This completed one of the very important stages in bringing the information capabilities of telecommunications closer to the possibilities of direct exchange of information between people. This stage covers all types of messages that are transmitted and received by the organs of vision, hearing, movement, facial expressions and gestures.

Only the information received and given out by a person with the help of the organs of touch and smell remained uncovered. But this part of the information is relatively small, and there is every reason to believe that over time it will be possible to transmit it using telecommunications. There are already some achievements in this direction. In the perfume industry, for example, an “electronic nose” (a device for assessing the smell of perfumes) is being tested, and in the food industry, an “electronic mouth” (a device for tasting wines). Therefore, there is hope that over time, communications will ensure 100% transfer of information obtained through direct interaction between people and with the outside world.

Based on the foregoing, we can conclude that the driving force behind the emergence and development of new types of telecommunications is the desire to bring the information content of telecommunications as close as possible to the conditions of direct communication.

Summarizing these arguments, we can state that the development of telecommunications began with low-speed transmission of text messages (telegraphy), then telephone communication appeared, requiring high transmission speeds, after that - transmission of still images (fax), sound (audio) broadcasting, video broadcasting (television ), video teleconferencing based on the use of multimedia technologies with a virtual reality effect, and for each subsequent type of communication higher transmission speeds were required. Thus, there is an obvious trend - as new types of telecommunications emerge, the speed of information transfer increases. This trend is also confirmed by economic considerations.

3. What are the prospects for the further development of types of telecommunications?

Based on the above, the question may arise: will the development of communication stop there? No, not only will it not stop, but it will not even slow down, and, moreover, it will happen at a faster pace. And that's why.

Firstly, we examined only the sequence of creation of new types of communications, but did not touch upon the development of the services provided with their help. But it is quite obvious that low quality of services can reduce the information content of any type of communication to zero. Therefore, one of the main directions for the development of telecommunications remains increasing the number of services and improving their quality.

This process will take place on the basis of new technologies: integrated and intelligent networks, personal and mobile communication networks, multimedia, new guiding systems and transmission methods, information compression, etc. But at the same time, telephony will remain telephony, no matter what it is called (for example, computer telephony, telephone mail), and data transmission - data transmission, etc.

At the same time, it will be necessary to resolve issues related to reducing costs and tariffs for communication services.

The solution to these problems largely depends on the development of electronics and computer technology. At the same time, when assessing the quality of all types of communication, the same parameters are used as for assessing the quality of information transmission during direct communication, and the main requirement is to bring the quality of communication services as close as possible to the quality of transmission during direct communication. True, in the first case, requirements for delivery to the address and time of transfer are also added.

Secondly, all of the above applies only to the transfer of information in a point-to-point system (between two people). However, a person can simultaneously communicate not with one person, but with many people (the “point - many points” system). Communication can also take place according to the “many points - many points” scheme (meaning a mass of people).

And, finally, thirdly, we limited ourselves to considering only those cases when the source and consumer of information is a person, whereas now a computer is widely and increasingly acting in this capacity. Moreover, teleprocessing systems and telematics services will increasingly use telecommunication services and, first of all, services based on new technologies.

We only note that the services for computer-computer and human-computer communication are increasingly being improved and are approaching the quality of direct communication services, for example, the authentication service of the sender and recipient, an agreement on the method of work (simplex - duplex), on the possibility of receiving a message of a certain size , confidentiality.

4. Can telecommunications provide services beyond face-to-face communication between people?

When answering this question, we will only talk about those telecommunication services that are not available during direct communication between people or are of lower quality.

Let's consider a service such as transmission with re-reception and storage. This service is convenient in conditions where the sender and recipient are in places with different zone times or when it is impossible or inconvenient to transmit information earlier, and later it is not possible. Such services are provided by messaging services (e-mail), computer telephony and other telecommunications services.

Another situation may arise: the user wants to maintain the confidentiality of receiving information. In a direct meeting with this person, it can be very difficult to evade his intentions, while the computer telephony service provides this opportunity: when receiving a telephone call, the subscriber, before picking up the handset, by pressing a special button on the device, receives on the display not only the caller’s number, but also his photograph. Based on this information, he decides whether to pick up the phone or fake his absence. In simpler telephone systems, the calling phone number is displayed on the device's screen.

There is also such a service as a “closed group of subscribers”, which is provided by the message processing service. Its implementation in conditions of direct communication in larger mass people is very problematic.

In places where a large number of people gather (within immediate audibility and visibility, when there are no means of communication), the exchange of different types of information (speech, text, still and moving images) can take place.

Communication systems such as audio and video conferencing not only fully ensure the remote exchange of all listed types of information, but also create additional features, in particular, the transfer of some information only to a certain group of participants.

Great opportunities communication compared to direct communication between person and person or person and computer should not be surprising. We are already accustomed to the fact that a microscope, telescope, car, airplane, etc. expand our capabilities.

Bibliography

Shvartsman V. O. Telecommunications and information // Telecommunications. – 1997. – No. 5.

Page 32 from 32 History of the development of telecommunication systems and computer networks

History of the development of telecommunication systems and computer networks

Computing and telecommunications technologies

Computer network (Computer network) is a collection of computers connected by communication lines. Communication lines are formed by cables or wires, p-channels and optical communication devices. All network equipment operates under the control of system and application software.

Net - network - an interacting set of objects formed by data transmission and processing devices.

Computer networks are by no means the only type of networks created by human civilization. Even the aqueducts of Ancient Rome can be considered one of the most ancient examples of networks covering large areas and serving numerous customers. Another, less exotic example is electrical networks. In them you can easily find analogues of the components of any territorial computer network: sources of information resources correspond to power plants, highways - high-voltage power lines, access networks - transformer substations, client terminals - lighting and household electrical appliances.

On the one hand, networks are a special case of distributed computing systems in which a group of computers coordinately performs a set of interrelated tasks, exchanging data automatically. On the other hand, computer networks can be considered as a means of transmitting information over long distances, for which they use data coding and multiplexing methods that have been developed in various telecommunication systems

Let's consider the main stages of development of telecommunication networks.

In the middle of the 20th century. basic communication systems (lat. communico - I make it common) between people involved in the economy, not counting the usual postal letters, there were telegraph, telephone and radio communications. Television was in its infancy. Information flows were transmitted through telegraph, telephone and radio networks, but the processing of the transmitted information was entirely entrusted to humans.

The invention of the computer was a real breakthrough in science, technology, economics and social life. In the first stages of its development (until the 70s of the 20th century), computer technology was used exclusively for processing information, and the collection and transmission of information was carried out using telecommunication systems and networks, the basis of which was the above-mentioned telegraph, telephone networks and radio networks.

After the creation of computer networks, which are a collection of computers and communication channels connecting them, the collection, transmission and processing of information began to be carried out using computer technology. Two evolutionary paths - the development of telecommunications and computer technology - led them to a natural connection.

Telecommunication systems and networks are “old-timers” compared to computer networks, and the first of them were telegraph and telephone networks.

Telegraph (Greek tele - far and grapho - writing) was invented in the middle of the 19th century. and was intended to transmit messages over a distance using electrical signals, symbols and letters. The most notable contribution to the development of the telegraph was made by such scientists as K. Steingeil, W. Siemens, S. Morse, J. Baudot and others.

In 1838, in Munich, the German scientist K. Steingeil built the first telegraph line 5000 m long.

In 1843, Scottish physicist A. Bain demonstrated and patented his own design of an electric telegraph, which made it possible to transmit images over wires. A. Bane's machine is considered the first primitive fax machine.

In 1866, a transatlantic telegraph cable was laid along the ocean floor between America and Europe, and in 1870, the Siemens company extended an Indo-European telegraph line 11 thousand km long.

At the end of the 19th century. In Europe, 2840 thousand km of underground cable of telegraph lines were stretched, in the USA - over 4 million km, in Russia the length of telegraph lines was 300 thousand km. The total length of telegraph lines in the world at the beginning of the 20th century. amounted to about 8 million km.

By the middle of the 20th century. In Europe, telegraph networks were created, called Telex (TELEgraph + EXchange). Somewhat later, a national subscriber telegraph network was also created in the USA, similar to Telex and called TWX (Telegraph Wide area eXchapge).

International subscriber telegraph networks* were constantly expanding, and by 1970 the Telex network united subscribers from more than 100 countries.

Nowadays, the ability to exchange messages over the Telex network has been preserved largely thanks to Internet e-mail. In the territory of the former USSR, telegraph communications still exist. Telegraph messages are transmitted and received using special devices - telegraph modems, interfaced in communication centers with personal computers of operators. Telegraph communications are used mainly for the transmission of telegraph correspondence coming from state enterprises, institutions and individuals, conducting documentary negotiations, transmitting statistical data and various digital information between enterprises.

However, in some countries, national operators considered the telegraph an outdated form of communication and curtailed all operations for sending and delivering telegrams. In the Netherlands, telegraph communications ceased operation in 2004. In January 2006, the oldest American national operator, Western Union, announced a complete cessation of services to the population for sending and delivering telegraph messages. At the same time, in Canada, Belgium, Germany, Sweden, Japan, some companies still support the service for sending and delivering traditional telegraph messages.

Historically, telephone networks appeared somewhat later than telegraph networks.

The first words were spoken by phone (Greek tele - far and phone - voice) March 10, 1876 and they belonged to the Scottish inventor, teacher of the school for the deaf and dumb Alexander Graham Bell: “Mr. Watson, come in, I want to see you.” The range of this telephone line inside the building was 12 m. It should be noted that at first the telephone was underestimated by telegraph specialists, who perceived the telephone as “an unnecessary laboratory toy*. This expert assessment was an example of the largest and most serious mistake in the entire history of the telecommunications business. Within a few years, the telephone and telephone networks began to develop at a rapid pace.

In 1878, the Bell Telephone company, organized by A.G. Bell in New Haven (Connecticut, USA), the world's first telephone exchange was built and the first telephone directory of 21 pages was published, and the very next year the same company began construction of a telephone network for 56 thousand subscribers.

The first long-distance telephone network in Russia started operating in 1880 on the Tsarskoye Selo Railway. Having appreciated the advantages of the new type of communication, Russian entrepreneurs began to petition the government for permission to build telephone lines.

The first telephone exchange subscribers were connected manually and it was possible to call a subscriber by calling the required number to the telephone operator. In the 10s. XX century automatic telephone exchanges (ATS) gradually began to replace telephone operators who connected subscribers manually. Telephones with rotary dialing appeared. The first automatic telephone exchange in the USSR appeared only in 1924 in the Kremlin and served 200 subscribers. The city Moscow telephone exchange for 15 thousand subscribers began operating in 1930. By the beginning of World War II, there were more than 1 million subscribers in the USSR.

After World War II, the development of telephone networks received new impetus. In 1951, for the first time in the USA, automatic telephone exchanges began to be used not only for connections within one city, but on intercity lines. In the USSR, such an automatic telephone exchange was first put into operation in 1958 between Moscow and Leningrad.

In 1956, 90 years after the first telegraph cable line was laid across the Atlantic, the first transatlantic telephone line, connecting the UK and the US (via Canada), was completed.

In the 50-60s. XX century basic methods of digital signal transmission, including voice, were developed, work was carried out to create radio and video telephony, and mobile telephony.

In 1978, Bahrain began operating a commercial cellular telephone system, which is considered the first real cellular telephone system in the world.

80-90s XX century characterized by intensive implementation digital methods voice transmission and related telephone networks, the use of satellite communications, mobile cellular communications, as well as the widespread use of computers to ensure the functioning of telephone networks.

Works in the area radio communications began when the German scientist G. Hertz in 1888 discovered a method for creating and detecting electromagnetic radio waves. April 25, 1895

Russian scientist A.S. Popov gave a report on the method of using radiated electromagnetic waves for wireless transmission of electrical signals containing information. In March 1896, the scientist conducted an experiment; he transmitted a radiogram with two words “Heinrich Hertz” at 250 m. A few years later in Kronstadt, without applying for a patent, he launched the production of receiving and transmitting equipment. The enterprising Italian G. Marconi became interested in the new invention. In July 1898, he filed a patent in England, presenting a similar device, slightly complicating A.S.’s circuits. Popova. The priority of the discovery of radio remained in the history of mankind with G. Marconi.

In 1898, G. Marconi organized radio communications between France and England, and in 1901 he managed to transmit signals from a station in England to a station in Newfoundland, USA. At the beginning of its development, radio communications were used to transmit telegraph messages, without taking into account the radio's ability to transmit sound.

In 1915, a historic experiment was carried out when speech signals were successfully transmitted by radio from Arlington, Virginia, to Paris. It should be noted that G. Marconi preferred that cornerstone his wireless telegraph remained Morse code, since he did not see any useful application for wireless speech transmission.

In 1920, the American radio amateur Conrad designed a radio station to operate in “telephone” mode and began broadcasting for the first time in the world.

In the first half of the 20th century, after scientists and engineers developed more advanced amplification equipment, antenna devices, as well as methods for transmitting and receiving radio signals, radio communications began to develop rapidly.

Second half of the 20th century was characterized by the improvement of radio equipment, the development of digital radio communication methods, as well as the use of satellite radio communication systems.

Concerning television (“radio with image”), then the ideas of creating an electrical system for transmitting moving images over a distance were expressed back in the 70s.

XIX century These ideas were based on purely theoretical conclusions, since the possibilities of physical experiments at that time were negligible. However, in the mid-20s. XX century The industrial and technical base has developed so much that for the first time it became possible to practically implement the theoretical principles of television.

Ideas and experiments on transmitting a moving image over a distance were preceded by ideas and experiments on transmitting a still image.

In the 20s XX century the development of electronic television took place in the fight against the opposition of supporters of mechanical television (using rotating mechanisms to obtain a scan on the screen), who were pessimistic about the prospects electronic systems due to the great technical difficulties associated with their creation. But the idea of ​​electronic television, as the most progressive, turned out to be the most vital.

The father of modern electronic television was V.K. Zvorykin, who emigrated to the United States after the Civil War. In 1931, he invented a cathode ray tube, which he called an iconoscope. The invention of the iconoscope was a turning point in the history of television, determining the direction of its further development; he provided television broadcasts from a large number lines.

The first transmissions of television images over a radio channel in the USSR were made in April-May 1931. They were carried out, however, with the image decomposed into lines according to mechanical system, i.e. The image was scanned into elements using a rotating disk.

Research in the field of transmitting and receiving cathode ray tubes, scanning device circuits, amplifiers, television transmitters and receivers, and advances in radio electronics prepared the transition to electronic television systems.

In the USSR, in the summer of 1938, the experienced Leningrad television center was the first to start operating, and in Moscow, on Shabolovka, a special building was built; television equipment and a transmitter were ordered from the USA, and leading specialists underwent training there. As a result, the first Moscow television center appeared in the country, accepted into permanent operation in December 1938.

In 1953, regular color television broadcasting began in the United States, but due to the high cost of color televisions, it became widespread only after 12-15 years (the first 10 million televisions were sold by 1966). In the USSR, regular broadcasting in color began only in 1967, Central Television programs became color in 1977, and peripheral television centers received color equipment in 1987.

In the early 90s. XX century transmission research has begun digital signal via over-the-air communication channels. This technology has gained recognition in a short time. Currently, it is used by more than 300 television electronics manufacturing companies.

Along with terrestrial television, work was carried out around the world to create systems cable television . The first cable television system in the United States was built in 1952 in Lunsford to receive broadcasts from the nearby television center in Philadelphia. The reason for the emergence of cable television in the United States in 1948 was the suspension of the issuance of licenses for new television transmitting stations for almost four years. However, due to its high quality and noise immunity, cable television has become the main type of television in large cities.

In the 1960s - 1970s. In the USSR, in accordance with the concepts of the development of television broadcasting, a huge, almost total system of collective television reception was created - almost 80% of television viewers in cities received television via coaxial cable.

In recent years, cable television has become one of the most dynamically developing areas of telecommunications networks. The advantage of television cable networks is that they can also be used to access the global Internet or transmit information from energy and water meters.

The radio and television systems discussed above using radio channels for data transmission are the main elements of wireless telecommunications systems, including satellite systems and mobile cellular communication systems.

History of the development of computer networks

Computer networks are the logical result of the evolution of computer technology. The ever-increasing needs of users for computing resources have led to attempts by computer technology specialists to combine individual computers into a single system.

Let's look first at the computer root of computer networks. First computers 50s - large, bulky and expensive - intended for a very small number of selected users. Often these monsters occupied entire buildings. Such computers were not designed for interactive user work, but were used in batch processing mode.

Batch processing systems, As a rule, they were built on the basis of a mainframe - a powerful and reliable general-purpose computer. Users prepared punched cards containing data and program commands and transferred them to the computer center (Fig.).

Operators entered these cards into a computer, and users usually received printed results only the next day. Thus, one incorrectly filled card meant at least a day's delay. Of course, for users an interactive mode of operation, in which they can quickly manage the processing of their data from the terminal, would be more convenient. But the interests of users were largely neglected in the early stages of the development of computing systems. The focus was on the efficiency of the most expensive device in a computer, the processor, even to the detriment of the efficiency of the specialists using it.

In the early 60s. XX century Interactive (with user intervention in the computing process) multi-terminal time sharing systems began to develop. In such systems, a powerful central computer (mainframe) was placed at the disposal of several users. Each user received at his disposal a terminal (a monitor with a keyboard without a system unit), with the help of which he could conduct a dialogue with the computer. The computer processed the programs and data coming from each terminal in turn. Since the computer's response time to the request of each terminal was quite short, users practically did not notice the parallel operation of several terminals and they created the illusion of exclusive use of the computer. Terminals, as a rule, were dispersed throughout the enterprise, and information input and output functions were distributed, but information processing was carried out only by a central computer.

Such multi-terminal centralized systems superficially resembled local computer networks, the creation of which in reality still had a long way to go. The limiting factor for the development of computer networks was primarily the economic factor. Due to the high cost at that time, enterprises could not purchase several computers at once, which means there was nothing to connect into a computer network.

The first networks are global

The development of computer networks began with the solution of a simpler problem - access to a computer from terminals located many hundreds, or even thousands of kilometers away from it. In this case, the terminals were connected to the computer through telephone networks using special devices - modems. The next stage in the development of computer networks was connections via modem not only “terminal-to-computer”, but also “computer-to-computer”. Computers have the ability to exchange data automatically, which is the basic mechanism of any computer network. Then, for the first time, the possibility of exchanging files, synchronizing databases, using e-mail, i.e. appeared on the network. services that are now traditional network services. Such computer networks are called global computer networks.

Global networks ( Wide Area Networks , WAN ) – networks connecting geographically dispersed computers, possibly located in different cities and countries.

It was during the construction of global networks that many of the basic ideas underlying modern computer networks were first proposed and developed. Such, for example, as the multi-level construction of communication protocols, the concepts of switching and packet routing.

Global computer networks have inherited a lot from other, much older and more widespread global networks - telephone networks. The main technological innovation that the first global computer networks brought with them was the abandonment of the circuit switching principle, which had been successfully used in telephone networks for many decades.

A composite telephone channel allocated for the entire duration of a communication session, transmitting information at a constant speed, could not be effectively used by pulsating computer data traffic, in which periods of intense exchange alternate with long pauses. Field experiments and mathematical modeling have shown that pulsating and largely insensitive computer traffic is transmitted much more efficiently by networks operating on the principle of packet switching, when data is divided into small portions - packets - which independently move through the network due to the presence of the end node address in the packet header.

Since laying high-quality communication lines over long distances is very expensive, the first global networks often used existing communication channels that were originally intended for completely different purposes. For example, for many years, global networks were built on voice-frequency telephone channels capable of carrying only one conversation in analog form at a time. Because the transmission speed of discrete computer data over such channels was very low (tens of kilobits per second), the range of services provided in wide area networks of this type was usually limited to file transfers, mainly in the background, and e-mail. In addition to low speed, such channels have another drawback - they introduce significant distortion into the transmitted signals. Therefore, the protocols of global networks built using communication channels Low quality, are distinguished by complex procedures for monitoring and data recovery.

Historically, the first computer networks were created by the agency for the protection of advanced research projects DARPA on behalf of the US military department. In 1964, the concept and architecture of the world's first computer network, ARPAnet (from English: Advanced Research Projects Agency Network), was developed; in 1967, the concept of “computer network protocol” was first introduced. In September 1969, the first computer message was transmitted between computer nodes at California and Stanford universities. In 1977, the ARPANET network consisted of 111 nodes, in 1983 - 4 thousand. The network connected computers different types, running various operating systems with additional modules that implemented communication protocols common to all computers on the network. Such operating systems are considered the first network operating systems. The ARPANET ceased to exist in 1989.

The progress of global computer networks was largely determined by the progress of telephone networks.

Since the late 60s, telephone networks have increasingly used digital voice transmission.

This led to the emergence of high-speed digital channels connecting automatic telephone exchanges (PBX) and allowing the simultaneous transmission of tens and hundreds of conversations. A special technology has been developed to create so-called primary, or support networks. Such networks do not provide services to end users; they are the foundation on which high-speed point-to-point digital channels are built, connecting the equipment of other, so-called overlay networks, which already work for the end user.

At first, primary network technology was exclusively an internal technology of telephone companies. However, over time, these companies began to lease part of their digital channels formed in primary networks to enterprises that used them to create their own telephone and global computer networks. Today, primary networks provide data transfer rates of up to hundreds of gigabits (and in some cases up to several terabits) per second and densely cover the territories of all developed countries.

By the end of the 1970s, the APRAnet network already included about 200 end systems. After 10 years, the number of hosts on the Internet, which already united many other computer networks, reached 100 thousand. Thus, the 1980s are characterized by the rapid spread of previously created network technologies.

In the early 80s there was an active unification local networks universities into large regional networks. Examples include the B1TNET network, which provided file and e-mail exchange between universities in the northwestern United States, CSNET, which united researchers in the field of network technologies independently of APRAnet, etc. In 1986, the NSFNET network was developed, which allowed access to the computing resources of supercomputers . The initial speed of the line, which was 56 Kbps, increased to 1.5 Mbps by the end of the decade. The NSFNET backbone made it possible to interconnect regional computer networks in the United States.

In the 1980s, APRAnet already contained many of the components that form the basis of the modern Internet. On January 1, 1983, the standard NCP protocol for data exchange between hosts was replaced by the TCP/IP protocol stack (RFC 801). Since then, the TCP/IP stack has been used by all Internet hosts. In the late 1980s, significant improvements were made to the TCP protocol to provide end systems with congestion control. In addition, the Domain Name System (DNS) was developed to associate the mnemonic names of Internet resources with their 32-bit addresses (RFC 1034).

In parallel with the development of APRAnet in the United States, the Minitel project arose in France in the early 1980s, which had support from the French government and set itself the ambitious goal of connecting all networks into a single computer network. The system developed by Minitel was an open packet-switched computer network (X.25 protocol with virtual channel support), consisting of Minitel servers and low-cost user terminals with built-in low-speed modems. Great success came to the Minitel project after the French government announced the distribution of free terminals to everyone for home use. The Minitel network contained both free and paid information resources. At the height of its popularity in the middle of the last decade, Minitel supported more than 20,000 types of services - from remote banking to providing access to specialized research databases.