For me personally, there is nothing more pleasant to be on a business trip in some other city and, after a busy day, chat with colleagues on various abstract topics over a cup of tea, beer and fish. One of these evenings we tried to restore the evolution of communications and the list of technologies and the names of people who, with their genius, gave impetus to the development of our frenzied information world. What I managed to remember - under the cut. But I got the impression that we missed a lot. Therefore, I am waiting for comments and interesting stories from you, dear Khabrovtsy.

Remembering from ancient times...

The party was in full swing when we began to remember the development of communication technology. The main idea is to remember everything that in one way or another was aimed at transmitting information messages between people. The first thing that everyone remembered (when they saw a colleague entering the room, whom we sent for another portion of foamy tea) was a messenger or messenger.

The history of the exchange of information messages begins from the Stone Age. Then the information was transmitted by the smoke of fires, blows to the signal drum, the sounds of pipes through a developed network of signal towers. Later they began to send messengers with oral news. Perhaps this is the very first and most effective way to convey an urgent message between people. Such a messenger memorized the "letter" from the words of the sender, and then retell it to the addressee. Egypt, Persia, Rome, the state of the Incas - had a developed, well-organized mail. Messengers plied the dusty roads day and night. They took turns or changed horses at specially built stations. Actually, from the Latin expression "mansio pozita ..." - "station at the point ..." the word "mail" came from. 2500 years ago, the relay method of transmitting letters from messenger to messenger was already used. In the last quarter of the 9th century, almost at the very beginning of the existence of Kievan Rus, the foundations of Russian mail were laid - one of the oldest in Europe. In one row with it in time of occurrence, only the communication services of Great Britain and Spain can be put. The courier service stands apart, the history of which in Russia goes back more than two centuries. However, this is a special type of communication that served exclusively government officials and the military.

Ancient letters are a recognized example of the culture of people's communication. Special paper was produced, perfumes for impregnating envelopes, clichés, sealing wax and seals - all this was in the order of things and writing a letter to another person was a whole ritual.

Pigeon mail

No matter how fast the messenger is, he cannot keep up with the bird. Carrier pigeons have made a huge contribution to human communication. A kind of short message service - after all, a dove could only carry a small load, a short letter or even a note. However, pigeon mail was a very effective information channel used by politicians, brokers, the military, and even ordinary people.

Device parameters
Flight range - up to 1500 km. (Competitions are held from a maximum distance of 800 km.)
Speed ​​- up to 100 km / h
Flight conditions - any (rain, snow, no matter how much)
Service life - up to 10-15 years (with good care)
Price - from $ 100 (the most expensive Danish Syubian pigeon named "Dolce Vita" was recently sold for 329 thousand dollars)

Passport of the most expensive pigeon (identification comes from the pupil of the bird)

Almost any pigeon can become a carrier. These birds have an amazing ability to find their way to the nest, but provided that he was born there, took to the wings and lived for about 1 year. After that, the pigeon can find its way to the house from anywhere, but the maximum distance cannot be 1500 km. It is still not clear how pigeons navigate in space. There is an opinion that they are sensitive to the Earth's magnetic field and infrasound. They are also helped by the sun and stars. However, there are also disadvantages. Pigeon mail is a simplex communication. Pigeons cannot fly back and forth. They are able to return only to the parent nest. Therefore, for information purposes, pigeons were taken away in special cages or cars to another place, where it was necessary to establish an “information channel”.


There are probably thousands of stories and legends about the role carrier pigeons played in human life. One of these is about the Rothschild family. The news of Napoleon's defeat at Waterloo in 1815 was received by Nathan Rothschild via a pigeon two days before the official news, which enabled him to successfully campaign on the stock exchange with French papers and get $ 40 million profit from this transaction in 1815 prices! Even in our time it is not bad. A typical example of the importance of information, especially in financial areas.

Maritime and military communications

The most important place for communication is the theater of war. Before the advent of the telegraph and wired telephone exchanges, semaphore systems were actively (surprisingly still) used. Both iconic and luminous.


The semaphore, or flag, alphabet has been used in the Navy since 1895. She was designed by Vice Admiral Stepan Makarov. The Russian flag alphabet contains 29 alphabetic and three special characters and does not include numbers and punctuation marks. The transmission of information in this type of communication is word by letter, and the transmission speed can reach 60-80 characters per minute. Strangely, since 2011, the Russian Navy has abolished the training of sailors in the semaphore alphabet, although in most maritime powers of the world it is a mandatory discipline.
The signaling system with the help of special flags is also interesting. Used by ships. Only 29 pieces, which, as I understand it, everyone who goes to sea should know. Here, for example, are the first six flags. Some are quite funny.

Wired connection. Telegraph, telephone, teletype...

Let's talk about electrical systems. Of course, let's start with the telegraph. One of the first attempts to create a means of communication using electricity dates back to the second half of the 18th century, when Lesage built an electrostatic telegraph in Geneva in 1774. In 1798, the Spanish inventor Francisco de Salva created his own design for an electrostatic telegraph. Later, in 1809, the German scientist Samuel Thomas Semmering built and tested an electrochemical telegraph. The first electromagnetic telegraph was created by the Russian scientist Pavel Lvovich Schilling in 1832.

Of course, at this time, the infrastructure of wired communication began to develop rapidly. The appearance of the Morse apparatus and the clever patenting of the telephone by Bell (disputes about who nevertheless invented the very principle of the telephone has not yet faded away) led to the first wave of informatization of the planet. It was an amazing time of development of new technologies, which gave tens of thousands of jobs. Telephone operators, technicians, engineers, telephone and telegraph companies.

By the way, about telephone operators. The requirements for applicants were high. The girl must be smart, have an excellent memory and be pretty. Probably, such a requirement was because the heads of telephone exchanges in those days were only men.
Of course, companies producing various telegraph equipment began to develop rapidly. Peculiar technological startups of the 19th century).

Of course, it was important for the development of communication to introduce ordinary people to them. It was not uncommon to see such promotions on the streets of cities. Phone booth on wheels. Just like now.

And, of course, people were interested in the task of transmitting graphic information. Since the invention of the telegraph, work began on the transmission of images. Mainly photographs. The first prototypes of fax machines were being developed. However, it was only after the Second World War that an acceptable phototelegraph apparatus was made. And to transfer the image by phone and at all in the sixties. One way or another, these technologies have appeared and we are no longer surprised by them.

As I understand it, in the upper right corner is the eyepiece of a video camera, and behind the screen is equipment for image transmission. Cumbersome, apparently, was the system)

invention of radio

The real breakthrough in technology came after the invention of radio. Thanks to this, it was possible to get rid of wires and establish communications almost all over the planet. Of course, in the first place, this technology hit the military. Almost immediately, radio began to supplant the wired telegraph. But, of course, not immediately. The first radio equipment was unreliable and extremely expensive.

STRUCTURE AND ORGANIZATION OF MOBILE COMMUNICATIONS

Discipline of specialization of the specialty 200700 - Radio engineering

Graduating department "High-frequency means of radio communication and television"

The course was developed and taught by Associate Professor of the Department of HCRT, Ph.D. S.N. Shabunin

Goals and objectives of the discipline

The purpose of teaching the discipline "Structure and organization of mobile communications" is to study by students the current state of mobile radio communications, the architecture and functioning of paging systems, trunking and cellular communications, satellite communications systems.

Peculiarities of radio wave propagation in urban conditions, ways to improve the quality of radio channels are considered.

Requirements for the level of mastering the content of the discipline

The study of the discipline "Structure and organization of mobile communications" requires knowledge of previously read courses "Device for generating and generating signals", "Device for receiving and processing signals", "Antennas and microwave devices", "Electrodynamics and propagation of radio waves", "Digital devices and microprocessors" .

AT as a result of studying the discipline, students should:

have an idea about the main communication standards and the structure of networking;

be able to predict the passage of radio waves in mobile communication systems of various types;

choose a frequency plan for building communication networks;

calculate the number of users in a network cell;

choose for specific conditions the optimal scheme for organizing mobile radio communications.

1. Zakirov S.G. Cellular communication of the GSM standard. Current state, transition to third generation networks / S.G. Zakirov, A.F. Nadev, R.R. Faizullin. M.: Eco-Trend. 2004. 264 p.

2. Gromakov Yu.A. Standards and systems of mobile radio communication / Yu.A. Gromakov. M: Eco-Trend. 2000 240 p.

3. Andrianov V.I. Mobile communications. IN AND. Andrianov, A.V. Sokolov. St. Petersburg: BHV-St. Petersburg, 1998. 256 p.

4. Burnev V.B. Electronic textbook on the system of cellular communication with time division of channels of the GSM standard.http://study.ustu.ru/view/aid_view.aspx?AidId=50

5. Burnev V.B. Electronic methodological manual for the study of the standard of the cellular communication system IS-95c (CDMA-2000 1x). http://study.ustu.ru/view/aid_view.aspx?AidId=47

6. Antenna-feeder devices of land mobile communication systems / Ed. A.L. Buzova. M.: Radio and communication. 1997. - 150 p.

7. Ratynsky M.V. Fundamentals of cellular communications / M.V. Ratynsky. M: Radio and communications. 2000. 248 p.

8. The Free Encyclopedia http://en.wikipedia.org/wiki/GSM

9. The Free Encyclopedia http://en.wikipedia.org/wiki/Cdma

10. http://sabitov.pochta.ru/html/glava2.htm#General%20information

11. The Free Encyclopedia

http://en.wikipedia.org/wiki/Nordic_Mobile_Telephone

1. HISTORY OF THE DEVELOPMENT OF COMMUNICATIONS ..............................................................
2. PERSONAL RADIO COMMUNICATION .................................................................................. ................................................. ...
2.1. With PERSONAL CALLING SYSTEMS.....................................................................................................................
2.2. With TUNING SYSTEMS..........................................................................................................................
2.3. With CELLULAR COMMUNICATION SYSTEMS....................................................................................................................................
2.4. With SATELLITE COMMUNICATION SYSTEMS...........................................................................................................................
3. PERSONAL CALLING SYSTEMS .............................................................. ................................................. ...........
3.1. With METHOD FOR FORMING A WORKING AREA:.............................................................................................................
3.2. With STRUCTURE OF THE PACING NETWORK..........................................................................................................
3.3. F FUNCTIONAL PAGER SCHEME..................................................................................................................
3.4. With CODING STANDARDS IN PERSONAL CALL SYSTEMS.................................................................
4. CELLULAR MOBILE COMMUNICATION SYSTEMS .............................................................. ................................................. ..
4.1. With METHOD OF DIVISION OF THE TERRITORY INTO CELLS.............................................................................................................
4.2. T RI GENERATIONS OF MOBILE RADIO COMMUNICATION SYSTEMS.........................................................................................
5. ANALOGUE CELLULAR COMMUNICATIONS .............................................................. .................................................
5.1. BUT CELLULAR TAX SYSTEM NMT-450 ............................................... ...............................................
5.2. INCOMING CALL SETUP - BASE STATION TO MOBILE ................................................
5.3. OUTGOING CALL SETUP - MOBILE TO BASE ..............................................
5.4. O ORGANIZATION OF CONNECTIONS AND PRINCIPLES OF ADDRESSING SUBSCRIBERS.................................................................
5.5. With STANDARD WORKING FRAME STRUCTURE NMT ............................................... ................................................
5.6. E MOBILE STATION STAFET TRANSMISSION.................................................................................................
6. DIGITAL CELLULAR COMMUNICATION STANDARDS.................................................................. ................................................. .
6.1. GSM (GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS) .............................................. .........................................
6.1.1. Basic elements of a GSM network .............................................................. ................................................. ................
6.1.2. System operation .................................................................. ................................................. ...................
6.1.3. Checking the legality of the operation of the mobile station .............................................. .................................
6.1.4. Temporary frame structure .................................................................. ................................................. .................
6.1.5. Working time intervals (slots).................................................. ................................................. ........
6.1.6. Characteristics of the signal envelope .......................................................... ................................................. .....
6.1.7. Frequency hopping mode............................................................... ................................................. .................
6.1.8. Logical channels in the GSM standard.................................................... ................................................. ......
6.1.9. Structure of logical control channels .......................................................... ...............................................
6.1.10. Speech processing in the GSM standard .............................................. ................................................. ........
6.1.11. Channel coding .................................................................. ................................................. .........................
6.1.12. Radio signal modulation .................................................................. ................................................. .......................
6.1.13. Ensuring security in GSM .............................................................. ................................................. .........
6.1.14. Authentication mechanisms.................................................................... ................................................. ...............
6.1.15. Confidentiality of data transmission .................................................................. ................................................. .............
6.1.16. Prospects for GSM................................................... ................................................. .................................
6.2. With COMMUNICATION SYSTEMS WITH NOISE-LIKE SIGNALS..........................................................................................
6.2.1. DSSS (Direct Sequence Spread Spectrum) .................................................... ................................................. ......
6.2.2. MC-CDMA (Multi Carrier - CDMA).................................................. ................................................. ................
6.2.3. FHSS (Frequency Hopping Spread Spectrum) .................................................... ..................................................
6.2.4. CDMA (IS-95) cellular communication system .......................................... ................................................. .........
6.2.5. Traffic and control channels .......................................................... ................................................. .................
6.2.6. Direct Channels in CDMA IS-95............................................... ................................................. ...................
6.2.7. Forward channel coding .................................................................. ................................................. .................
6.2.8. Back channel coding .................................................................. ................................................. ..............
6.2.9. Signal conditioning by the base station............................................................... ..................................................
6.2.10. Signal conditioning by the base station............................................................... ...............................................
6.2.11. Power management .................................................................. ................................................. .........................
6.2.12. Formation of a QPSK signal............................................... ................................................. ................
6.2.13. Speech coding .................................................................. ................................................. ...................................

6.2.14. Combating multipath .............................................................. ................................................. ....................
6.2.15. Organization of the handover .............................................................. ................................................. ......
6.2.16. Security Aspects in IS-95............................................................... ................................................
6.2.17. Prospects for CDMA.............................................. ................................................. ...............................
7. RADIO WAVE PROPAGATION IN MOBILE COMMUNICATIONS.................................................................. .........................
7.1. R RADIO WAVES PROPAGATION IN FREE SPACE........................................................................
7.2. T RI OF THE MAIN METHODS OF RADIO WAVE PROPAGATION.............................................................................
	ABOUT RADIO WAVE REFLECTION ............................................................... ................................................. ......................
	D IFRACTION OF RADIO WAVES ............................................... ................................................. .........................
	SCATTERING OF RADIO WAVES ............................................... ................................................. .........................
7.3. MODELS FOR CALCULATION OF SIGNAL REDUCTION IN RADIO CHANNELS BASED ON EXPERIMENTAL
	.....................................................................................................................................................................
8. MULTI-STATION ACCESS TECHNIQUE.................................................................. .........................................
8.1. METHODS .................................................. ................................................. ....................... COMMUNICATION ORGANIZATIONS
8.2. FROM FREQUENCY DIVISION MULTIPLE ACCESS - FDMA SYSTEMS
8.3. FROM THE SYSTEM .................... TIME DIVISION MULTIPLE ACCESS - TDMA
8.4. FROM THE SYSTEM ................................ MULTIPLE ACCESS WITH EXPANDED FREQUENCY SPECTRUM
8.5. FROM THE SYSTEM ........................ FHMA MULTIPLE ACCESS
8.6. FROM THE SYSTEM ........................ CODE DIVISION MULTIPLE ACCESS - CDMA
8.7. COMPARISON .................................................. ......................................... CELLULAR COMMUNICATION NETWORKS BETWEEN THEM
9. SATELLITE............................................... ...........................PERSONAL COMMUNICATION SYSTEMS
9.1. ORGANIZATION .................................................... ................................................. ...................................... CONTACTS
9.2. H ISCOORBITAL................................................. ............................................... IRIDIUM COMMUNICATION SYSTEM
9.3. H ISCOORBITAL................................................. ...................................... GLOBAL STAR COMMUNICATION SYSTEM
9.4. GEOSTATIONAL ............................................................... ......................................... INMARSAT COMMUNICATION SYSTEM
10. ENVIRONMENTAL............................... ASPECTS OF THE USE OF MOBILE COMMUNICATIONS A
11. CONCLUSION............................................... ................................................. ................................................. ..
12. RESOLUTION............................................................... ................................................. ............................. EXERCISES

1. HISTORY OF DEVELOPMENT OF COMMUNICATIONS

The first mention of the transmission of information over a distance is found in the ancient Greek myth of Theseus. The father of this hero, Aegeus, sending his son to battle with the monster Minotaur, who lived on the island of Crete, asked his son, if successful, to raise a white sail on the returning ship, and in case of defeat, black. Theseus killed the Minotaur, but the sails, as always, were mixed up, and the unfortunate father, thinking that the monster had lifted his son, drowned himself. In honor of this event, the sea where the child-loving Aegeus drowned himself still bears the name Aegean. Drums, fire smoke, church bells were used to transmit messages, but such messages were not very informative.

The first communication system, called the telegraph, was invented by the Frenchman Claude Chappe (1763-1805) at the end of the 18th century. The first line was between Paris and Lyon. She worked as follows. Towers were built on the tops of the hills, on which special structures were installed with two long planks that changed their position. Each of the 49 positions corresponded to a letter or number. By the middle of the 19th century, the length of the lines had increased to 4828 km and the system worked quite successfully.

The next major step towards improving the means of communication was the appearance of the electric telegraph by Wilman Cook (1806 - 1879) and Charles Winston (1802 - 1875). Electrical signals were sent through wires that actuated arrows that pointed to various letters.

In 1843, American Samuel Morse (1791 - 1872) invented a new telegraph code that replaced the code of Wilman Cook and Charles Winston. Signals were transmitted in the form of dots and dashes. The reliability and accuracy of message transmission has increased significantly. Morse code is still used today.

The inventor of the telephone is Alexander Graham Bell, who on March 7, 1876 patented a method for transmitting sound by telegraph.

On April 25, Old Style (May 7, New Style), 1895, Alexander Stepanovich Popov, for the first time in the world, made a report to the scientific and technical community on the method he invented for using radiated electromagnetic waves for wireless transmission of electrical signals containing information useful to the recipient, and demonstrated such transfer in action. In March of the following year, he demonstrated a signal transmission device, transmitting a radiogram of their two words "Heinrich Hertz" to a distance of 250 m.

The first radiotelephone communication system, offering services to everyone, began its operation in 1946 in St. Louis (USA). The radiotelephones used in this system used conventional fixed

The content of the article

ELECTRONIC COMMUNICATIONS, the technique of transmitting information from one place to another in the form of electrical signals sent over wires, cables, fiber optic lines, or no guide lines at all. Directed transmission over wires is usually carried out from one specific point to another, as, for example, in telephony or telegraphy. Omnidirectional transmission, on the contrary, is usually used to transfer information from one point to many other points scattered in space, i.e. for broadcast purposes. Broadcasting is an example of non-directional transmission.

The transmission of signals over wires can be considered as the flow of electric current through a wire, which is interrupted or changed in any way, from a transmitter located at one of the points in the network. This interruption or change in current detected by the receiver at another point in the network is the signal or piece of information sent by the transmitter.

The transmission of information through radio or optical (light) waves is an electromagnetic radiation that can propagate without needing any medium, i.e. capable of propagating in a vacuum. Such transmission is carried out as a result of fluctuations in electric and magnetic fields. Radio and television waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays and gamma rays are all electromagnetic radiation. Each type of electromagnetic radiation is characterized by its own oscillation frequency, with radio waves corresponding to the low-frequency end of the spectrum, and gamma rays to the high-frequency end.

Although, in principle, signals can be transmitted by electromagnetic radiation of any frequency, not all parts of the electromagnetic spectrum are suitable for communication purposes, since the atmosphere is opaque for some wavelengths. The range of "radio frequencies" used is between about 1 and 30,000 MHz. In this range, AM broadcasts are broadcast at frequencies from 0.5 to 1.5 MHz, while FM and television broadcasts are broadcast over a much wider frequency range, the middle of which falls at 100 MHz. Microwave signals, including those sent to and received from communication satellites, are in the range from 4000 to 14000 MHz and even higher. Generally speaking, any signal needs a specific bandwidth or range of frequencies; the more complex the signal, the wider the required bandwidth. For example, a television signal, due to its much greater complexity, requires a bandwidth that is about 600 times greater than that of a voice signal. The entire used spectrum of radio frequencies allows placing 10 million speech or about 10,000 television channels in it. This spectrum is shared between broadcasters, emergency services, aviation, ships, mobile telephony, military and other users.

Revolution in the field of communication.

In recent decades, electronic communications have developed so rapidly that the words "revolution in the field of communications" do not seem to be an exaggeration. The basis for many innovations was the rapid progress of electronic engineering and technology. In the early 1950s, a device called the transistor was developed. This miniature electronic component, made of semiconductor materials, is used to amplify or control electric current. Because transistors are smaller and more durable than vacuum tubes, they replaced tubes in radios and became the basis of computers. TRANSISTOR.

In the late 1960s, instead of transistor circuits, computers began to use fully assembled semiconductor circuits, called integrated circuits (ICs). Subsequently, on a single silicon wafer, the size of which was only slightly larger than the size of the first transistor, technologists learned how to manufacture hundreds of thousands of transistors at once in a single process. This method, called large-scale integrated circuit (LSI) technology, allows many ICs to be placed in one small device.

Each stage of the development of electronics was accompanied by a significant increase in the reliability of electronic components. At the same time, it was also possible to significantly reduce the size, power consumption and cost of many types of electronic equipment.

The widespread use of technology such as computers, lasers, fiber optic lines, communication satellites, direct-dial telephones, video telephones, transistor radios, and cable television has led to a complete overhaul of the traditional classification of communication methods. Nowadays, wire transmission is practically not identified with direct address communication, and wireless transmission with radio broadcasting. Probably the most powerful influence on the development of communication technology was the significant increase in the capacity of communications both over the air and by wire. This increased bandwidth is used for the ever-increasing global traffic of television, telephony and digital information.

Laser.

One of the factors that played an important role in increasing the capacity of communication systems was the discovery of the laser in 1961. A laser is a light source that generates a narrow beam of high intensity light. Such a beam can be used to transmit signals. The unique feature of a laser is that it emits light of a single frequency, i.e. produces purely monochromatic radiation. Thus, a laser can serve as a generator of very high frequency (VHF) electromagnetic waves, similar to how a radio transmitter can serve as a source of lower frequency waves (radio waves). Since the frequency range of light waves (approximately from 5x10 8 to 10 9 MHz) is many times wider than the frequency range of radio waves, a light beam can transmit huge amounts of information. This part of the electromagnetic spectrum is wide enough to accommodate 80 million TV channels or 50 billion simultaneous telephone conversations.

Communication satellites.

The first communication satellites, placed in near-Earth orbits in the early 1960s, carried passive-type equipment and served only as signal repeaters.

Modern communications satellites are usually launched into a geostationary orbit at an altitude of 35,900 km above the Earth's surface. Each satellite has 10 or more microwave receivers and transmitters. A modern satellite makes it possible to transmit several television programs across the oceans to entire continents and to ensure the operation of more than tens of thousands of telephone channels.

Cables.

During World War I, communications engineers developed a method of using a pair of wires to transmit multiple telephone conversations at the same time. This method, called frequency multiplexing of channels, is based on the ability to transmit a wide range of audio frequencies over a pair of wires. In this case, the signals of each of the multiple transmitters are spread in frequency (using modulation) and the resulting higher frequency combined signal is transmitted to the receiving terminal, where it is separated into component signals by demodulation. A telephone cable with a protective sheath can contain from tens to hundreds of twisted wire pairs, each of which allows up to 24 telephone channels to operate.

However, cables consisting of wire pairs have certain limitations. Above a certain frequency, signals transmitted over one pair begin to interfere with the signals of an adjacent pair. To solve this problem, a new type of transmission medium was developed - coaxial cable. Such a cable, containing 22 coaxial pairs, can provide simultaneous operation of 132,000 telephone channels. Each pair in such a cable is a central wire enclosed in a tube of the second conductor. The center conductor and the tube are electrically isolated from each other.

TASI.

Time Division Multiplexing of Speech Interpolation (TASI) is a technique that doubles the capacity of transoceanic telephone cables by taking advantage of natural pauses in conversations. The two-way communication channel is idle for about 60% of the time during pauses in the conversation, as well as while the user is receiving. The TASI equipment, using a high-speed switch, provides unused time of one channel to any of the other users. Such a switch returns the channel to the user as soon as he starts talking, and disconnects him immediately after silence, providing the channel in pauses to other subscribers.

Pulse code modulation.

This method of signal transmission by means of digital technology is especially convenient when using LSI and VLSI, as well as fiber optic lines. Such digital (PCM) transmission of voice and TV signals will eventually replace other means of communication. When using pulse code modulation, speech or image signals can be divided into many small time intervals; at each interval, a series of pulses of constant amplitude represents a signal. These pulses are sent to the receiving station instead of the original signals. One of the advantages of PCM is related to the fact that discrete electronic pulses of constant amplitude are easily distinguished from random noise of arbitrary amplitude (electrostatic origin), which are present to one degree or another in any transmission medium. Such pulses can be transmitted substantially uninterrupted by ambient noise since they are easy to separate. PCM is used for a wide variety of signals. Telegraph and facsimile messages, as well as other data that was previously sent over telephone lines by other methods, can be transmitted much more efficiently in a pulsed form. The traffic of such non-speech signals is constantly increasing; there are also systems that allow the transmission of mixed signals of speech, data and video information.

Electronic switching.

Another innovation that has made telephony more efficient is electronic switching. The modern microcircuits described above made it possible to use electronic switches instead of mechanical ones at the PBX, which increased the speed and reliability of making calls. New switching systems are digital systems that use fast and compact LSIs to switch data, PCM signals or digital video signals. In addition to being well suited to various telephony applications, electronic switching allows for a number of innovations. These include: automatic transfer of a call to another number when the number of this subscriber is busy; speed dialing, in which the subscriber dials only one or two digits to connect to frequently called numbers; call signals, which notify the user that another subscriber is trying to connect with him.

Phones-computers.

The telephone of the future will be used not only for ordinary communication. Telephone sets with built-in miniature and inexpensive logic circuits will be able to perform complex electronic functions. With the help of a PBX, such a phone can become an individual computer. By pressing the keys of his telephone, the user will be able to enter the data he wants to store, process information, request data from some central file, or perform calculations.

Videophone.

New means of electronics make it possible to supplement sound information transmitted by telephone with images. Video transmissions between conference rooms located in several cities are used in order to avoid the need to move conference participants. Video broadcasts have begun to be widely used for teaching - lectures are transferred from one audience to another (remote) and recorded on videotape for use in the same purposes.

Cable television systems.

Although laser radiation and millimeter waves can be used for broadcasting, limitations due to atmospheric absorption and other types of interference can only be overcome at great cost. Therefore, when looking for ways to expand broadcasting to avoid the limitations associated with the use of electromagnetic radiation, cable systems are increasingly being used.

Cable television requires cabling from transmitters to receivers located in homes, for example. The radio listener or cable broadcast viewer does not experience the inconvenience of fading, ghosting and other interference. In addition, due to the fact that the number of channels transmitted via cable is practically unlimited (whereas a conventional TV broadcaster transmits only one program at a time), the viewer is provided with a much wider choice of programs. In the future, the media may become personalized information services capable of transmitting pre-recorded programs at the request of individual viewers.

Community cable television (CATV) systems have been in operation for many years. Originally intended to serve remote communities where rooftop antennas did not provide good signal reception, CATV systems are also widely used in cities where interference is a problem.

The computer as an intelligent assistant.

Computer scientists believe that eventually people will be able to communicate their ideas more effectively through computers than through direct conversation. Usually the purpose of the conversation is to exchange, compare and critically discuss ideas already formed in the minds of the participants in the conversation. Ideas are mostly expressed in words, but if the subject of discussion is complex or has technical specifics, then graphics, photographs and calculations have to be used. The conversation does not always lead to full understanding, since the concepts being expressed can not be easily expressed in words; often they contain data and associations that are linked together in such a complex way that even the speaker finds it difficult to fully understand and express them. The listener, on the other hand, is unable to examine the way the speaker thinks and must rely on the information that he provides, and with a degree of inadequacy that is difficult to assess.

The computer, according to cybernetics, provides the participant of the conversation with the opportunity to better understand the ideas of his interlocutor. A computer is an information processing machine that can store data, know where to find it, be able to compare it, sort it, compress it, or restructure it, and then display it on the screen in the most appropriate form. If information is entered into the computer that is relevant to the formulation of a certain idea, but did not sound sufficiently clear when the interlocutor explained this idea, then at the output of the computer one can get a general idea of ​​the speaker's way of thinking. Thus, the basic information of the speaker is available to the listener. In addition, the listener may need a computer to sort the data to reveal facts relevant to the problem or concept being discussed. Discussions can then take place between two or more interlocutors whose computers are connected so that information is collected, processed and exchanged so efficiently that solutions and creative ideas can emerge to a degree and at a level that could not be achieved without the use of computers. Experiments carried out in this direction have given encouraging results. OFFICE EQUIPMENT AND OFFICE EQUIPMENT; TELEPHONE; A COMPUTER;

Communication is an integral element of the existence of modern human society. In our technologically advanced age, we simply cannot imagine our lives without phones. But even a hundred years ago, a person could not even dream of such a luxury.

Until the middle of the 19th century, communication between Europe, England and America was established using steamship mail. But since this means of communication did not allow to receive news quickly, the human mind began to think about a more perfect solution to the problem.

The development of communications gained new momentum with the discovery by Volt in 1800 of the electric battery. The electrochemical telegraph was the first to be invented, it was thanks to him that it became possible to transmit messages from two different ends in a few hours, or even minutes.

The inventor of the telegraph, Semmering, used a gas that was released as a result of passing current through water (acidified). But the design was too complicated, Schweiger simplified it, but, nevertheless, message passing was too tedious a process.

In addition, alas, such a telegraph could only transmit written messages, so the inventors began to think about a more advanced version of the apparatus. Some attempts were made by the American physicist Page in 1837, but his invention only remotely resembled a telephone.

The development of communications received a new round thanks to the Reis telephone. He made about ten devices that could already partially transmit human speech, as well as music, but at the same time there was too high a signal was often muffled, and sometimes it was very difficult to make out what exactly they were saying at the other end.

He contributed to the development of communications, which began the construction of a new telephone. Together with his assistant, the inventor achieved his goal and was able to make an apparatus that more or less clearly began to transmit speech. But, unfortunately, the sound quality in such devices depended on the distance, the farther - the worse the audibility.

Over time, the phone has improved. The Russian Baron Schilling, the Englishman William Cook, the German inventor Steingel and many others worked on the development of this device. Before the phone took on its current form, it went through many tests. was marked by the advent of wireless communication devices, namely mobile phones, which perfectly transmit all sounds without any delay.

An equally important place in the development of communications is occupied by the invention of television communications and phototelegraphy. It was with the help of these means that video signals began to be transmitted. Initially, these were primitive sound and video transmitters, which later developed into color television. In the original version, the choice of programs and channels was small, but every year their number increases significantly.

But the classification will be incomplete if we do not remember the most global communication system, namely the Internet. Now we can't imagine our life without it. After all, it is thanks to him that you can easily find out all the news, keep abreast of events, pay for services, control almost all aspects of your life.

But it plays a decisive role in facilitating communication between people. After all, being thousands of kilometers apart, people can easily exchange photo, video and audio materials. See each other online, communicate in real time, without delays and delays.

Every year a person invents more and more new devices, modernizing existing ones and creating absolutely unique ones. Progress does not stand still, which means that the development of communications will not stop.

Human development is impossible without the exchange of information. For several hundred years, mail remained virtually the only way to deliver a message from point A to point B. However, with the discovery of electricity and electromagnetic fields, the situation began to change.

The emergence of wired and radio communications had a positive impact on the development of the world community. At the end of the 19th century, new means of data transmission appeared, which dramatically increased the speed of information exchange over long distances. Moreover, permanent communication between continents became possible. And yet, where did it all begin?

Timeline of communications development

Telegraph. In 1837, William Cook introduces the first wired electric telegraph with his own coding system. Later, in 1843, the famous Morse will present his development of the telegraph and develop his own coding system - Morse code. And already in 1930, a full-fledged teletype appeared, equipped with a telephone dialer and a keyboard like a typewriter.

Telephone. Alexander Bell patented in 1876 a device capable of transmitting speech over wires. By the way, the first telephones in Russia appeared in 1880. And in 1895, the Russian scientist Alexander Popov conducted the first radio communication session.

The discovery of the possibility of transmitting a signal by radio made a real revolution in the development of communications. Now it is possible to create a real global communication network. Indeed, with all the advantages of the first telephones and telegraphs, they had one drawback - wires. Now, thanks to the radio, it was possible to establish a constant connection with moving objects (ships, planes, trains) and establish intercontinental data transmission.

Pager and mobile phone. In 1956, the American company Motorola released the first pagers. This gadget is already forgotten and not used at the present time, and once it was a breakthrough in the communication industry. In 1973, the first mobile phone from Motorola appears. It weighs more than a kilogram and has impressive dimensions.

Computer network. Computer development began in earnest after World War II. Already in 1969, the first computer network, ARPANET, was created. It is generally accepted that it was this network that served as the basis of the modern Internet.

Global Information Network. At the moment, all means and types of communication are combined into one global telecommunications structure. The development of modern technologies allows you to connect to the worldwide network from almost anywhere on earth and get access to any necessary information.