Artificial means of communication. Wired communications
The content of the article
ELECTRONIC COMMUNICATIONS, a technique for transmitting information from one place to another in the form of electrical signals sent through wires, cables, fiber optic lines, or without any guide lines at all. Directed transmission by wire is usually carried out from one specific point to another, as in telephony or telegraphy. Undirectional transmission, on the other hand, is typically used to transmit information from one point to many other points scattered in space, i.e. for broadcast purposes. An example of non-directional transmission is radio broadcasting.
Wire transmission can be thought of as the flow of electrical current through a wire, which is interrupted or altered in some way, from a transmitter located at one point in the network. It is an interruption or change in current detected by a receiver at another point on the network and represents a signal, or piece of information, sent by the transmitter.
The transmission of information through radio or optical (light) waves is electromagnetic radiation that can propagate without the need of any medium, i.e. capable of spreading in a vacuum. Such transmission occurs as a result of oscillations of 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 vibration 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 ranges from about 1 to 30,000 MHz. In this range, AM radio broadcasts are carried out at frequencies from 0.5 to 1.5 MHz, and FM and television broadcasts are carried out in a much wider frequency range, the middle of which is at 100 MHz. Microwave signals, including those sent to and received from communications satellites, range from 4,000 to 14,000 MHz and even higher. Generally speaking, any signal requires a certain band or range of frequencies; Moreover, the more complex the signal, the wider the required frequency band. For example, a television signal, due to its much greater complexity, requires a bandwidth approximately 600 times greater than that of a speech signal. The entire radio frequency spectrum used allows it to accommodate 10 million voice or about 10,000 television channels. This spectrum is shared among broadcast stations, emergency services, aviation, ships, mobile telephony, military and other users.
A revolution in communications.
In recent decades, electronic communications have developed so rapidly that the words “communications revolution” do not seem like an exaggeration. The basis for many innovations was the rapid progress of electronic equipment and technology. In the early 1950s, a device called a transistor was developed. This miniature electronic component, made of semiconductor materials, is used to amplify or control electrical 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, computer technology began to replace transistor circuits with 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 to produce hundreds of thousands of transistors at once in one process. This technique, called large-scale integrated circuit (LSI) technology, allows multiple ICs to be housed in one small device.
Each stage of electronics development 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, communications satellites, direct dial telephones, video phones, transistor radios and cable television has led to a complete overhaul of the traditional classification of communication methods. Nowadays, wire transmission is practically no longer identified with direct address communication, and wireless transmission is no longer identified with radio broadcasting. Probably the most powerful influence on the development of communications technology was the significant increase in the capacity of communications, both over the air and by wire. This increased capacity is used for the ever-increasing global television, telephony and digital information traffic.
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 in the same way that a radio transmitter serves as a source of lower frequency waves (radio waves). Since the frequency range of light waves (approximately from 5-10 8 to 10 9 MHz) is many times wider than the frequency range of radio waves, a light beam can transmit enormous amounts of information. This part of the electromagnetic spectrum is wide enough to accommodate 80 million TV channels or support 50 billion simultaneous telephone conversations.
Communications satellites.
The first communications satellites, placed in low-Earth orbits in the early 1960s, carried passive equipment and served only as signal repeaters.
Modern communications satellites are typically launched into 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 oceans to entire continents and support the operation of more than tens of thousands of telephone channels.
Cables.
During World War I, communications technicians developed a method of using pairs of wires to transmit multiple telephone conversations simultaneously. This method, called frequency division multiplexing, is based on the ability to transmit a wide range of audio frequencies over a pair of wires. In this case, the signals from each of several transmitters are separated in frequency (using modulation) and the resulting higher-frequency combined signal is transmitted to the receiving terminal, where it is divided into component signals through demodulation. A jacketed telephone cable may contain tens to hundreds of twisted wire pairs, each capable of supporting up to 24 telephone channels.
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 the neighboring 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 second conductor tube. The center conductor and tube are electrically isolated from each other.
TASI.
Time multiplexed speech interpolation (TASI) is a technique that doubles the capacity of transoceanic telephone cables by exploiting natural pauses in conversations. The two-way communication channel is idle for approximately 60% of the time during pauses in the conversation, as well as while the user is working to receive. 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 begins to speak, and disconnects him immediately after silence, providing the channel in pauses to other subscribers.
Pulse code modulation.
This method of transmitting signals using 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 the signal. These pulses are sent to the receiving station in place of the original signals. One of the advantages of PCM is due to the fact that discrete electronic pulses of constant amplitude can be easily distinguished from random interference of arbitrary amplitude (electrostatic origin), which is present to one degree or another in any transmission medium. Such pulses can be transmitted essentially without interference from extraneous noise since they can be easily separated. PCM is used for a wide variety of signals. Telegraph and facsimile messages, as well as other data that were previously sent over telephone lines by other methods, can be transmitted much more efficiently in pulsed form. The traffic of such non-speech signals is continuously increasing; There are also systems that allow the transmission of mixed signals of speech, data and video information.
Electronic switching.
Another innovation that has led to increased efficiency in telephone communication is electronic switching. The modern microcircuits described above have made it possible to use electronic switches in PBX instead of mechanical ones, which has increased the speed and reliability of calls. New switching systems are digital systems that use fast, compact LSIs to switch data, PCM or video signals in digital form. In addition to being well suited for a variety of telephony applications, electronic switching allows for a number of innovations. These include: automatic call transfer to another number when the subscriber’s number is busy; speed dialing, in which the subscriber dials only one or two digits to connect to frequently called numbers; Call signals that notify the user that another subscriber is trying to connect to him.
Telephones and computers.
The telephone of the future will be used not only for ordinary communications. Telephones with built-in miniature, low-cost logic circuits will be capable of performing complex electronic functions. With the help of a PBX, such a phone can become an individual computer. By pressing the keys on his telephone, the user will be able to enter data he wants to store, process information, query data from some central file, or perform calculations.
Videophone.
New electronics make it possible to supplement audio information transmitted over the telephone with images. Video transfers between conference rooms located in several cities are used to avoid the need for conference participants to travel. Video broadcasts have begun to be widely used for training - lectures are transmitted from one audience to another (remote) and recorded on video tape for use for the same purposes.
Cable television systems.
Although laser radiation and millimeter waves can be used for broadcasting, limitations due to atmospheric absorption and various other types of interference can only be overcome at great cost. Cable systems are therefore increasingly being used to find ways to expand broadcasting without the limitations of electromagnetic emissions.
Cable television requires laying cables from transmitting to receiving stations located, for example, in homes. A radio listener or cable TV viewer does not experience inconvenience from fading, ghosting and other interference. In addition, due to the fact that the number of channels transmitted by cable is practically unlimited (whereas a typical TV broadcast station broadcasts only one program at a time), the viewer has 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 operating 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.
Computer as an intelligent assistant.
Computer scientists believe that eventually people will be able to communicate their ideas more effectively using computers than through direct conversation. Typically, the purpose of a conversation is to exchange, compare, and critically discuss ideas already formed in the minds of the participants in the conversation. Ideas are mainly expressed in words, but if the subject matter is complex or technical, then graphics, photographs and calculations must be used. Conversation does not always lead to full understanding because the concepts being presented may not be easy to express in words; they often contain data and associations that are interconnected in such a complex way that even the speaker finds it difficult to fully understand and express them. The listener is unable to investigate the speaker's way of thinking and must rely on the information that he communicates, and with a degree of inadequacy that is difficult to assess.
The computer, according to cyberneticists, provides the participant in a 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, can collate 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 clearly enough when the interlocutor explained this idea, then the output of the computer can give a general idea of the speaker's way of thinking. In this way, the speaker's basic information is made available to the listener. In addition, the student may need a computer to sort through data to identify facts relevant to the problem or concept being discussed. Discussions can then arise 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 arise to a degree and at a level that could not be achieved without the use of computers. Experiments carried out in this direction have yielded encouraging results. OFFICE EQUIPMENT AND OFFICE EQUIPMENT; TELEPHONE; COMPUTER;
1. Language as a means of communication.
2. Systems for transmitting information by sound means.
3. Systems for transmitting information by visual means.
Bibliography
1. Kule, K. Media in Ancient Greece. Works, speeches, research, travel / K. Kule. – M.: NLO, 2004. – 256 p.
2. Lovell, D. The Great Wall of China / D. Lovell. – M.: AST, 2008. – 442 p.
3. Ostrovsky, A.V. History of world and domestic communications: textbook. allowance / A. V. Ostrovsky. – St. Petersburg. : SPbSUT Publishing House, 2011. – pp. 6–21.
4. Thorpe, N. Secrets of ancient civilizations / N. Thorpe, P. James. – M.: Eksmo, 2007. – 864 p.
5. Hagen, V. Vf. Aztecs, Mayans, Incas. Great kingdoms of ancient America / V. Vf. Hagen. – M.: Tsentrpoligraf, 2012. – 538 p.
When considering the first question, it should be borne in mind that the desire to transmit information over the maximum possible, practically unlimited distance existed even before the emergence of early civilizations. Scientists noted that the first systems of information perception are hearing and vision. Communication between people began with individual sounds, gestures, and facial expressions, which laid the foundation for the simplest means of communication. Emphasize that all means of communication can be divided into two types: natural (language) and artificial (mechanical and electrical), which arose as a result of the development of human society.
In this regard, pay attention to the problem of anthropogenesis. Assess the role of the factors that complete the process of separating man from the animal world: man’s mastery of fire and the emergence of language, which can be considered as the first information revolution. Emphasize the difference between human language as a sign system and the “language” of other animals:
Human language has a social nature. Its formation and development is associated with the joint activity and communication of people 9 (in animals the “language” is innate, in humans it is acquired);
animal sign systems are closed. In some cases, animals can perceive new signs from humans and even successfully use the received symbols (chimpanzee monkeys were able to teach the language of deaf-mutes at the level of the vocabulary of a two-year-old child). However, animals cannot go beyond the limits of their acquired knowledge.
Human languages are open and capable of unlimited development: people invent new symbols, introduce them into communication, and store information with their help.
Moving on to the second question, please note that the need to transmit information in the context of increasingly complex forms of organization of human groups (herd, clan, tribe, tribal unions, policies, states, empires) influenced the evolution of the simplest means of communication. In addition to natural means of communication, mechanical (sound and visual) are beginning to be used.
Give examples of sound means of communication, which are divided into drums and winds.
Which of these means were used in Ancient Rus'?
When considering the third question, remember what applies to the simplest visual aids. Show why the simplest optical (from the Greek “visual perception”) communication was more advanced than sound signaling. List in what cases and what means of visual signaling were used in the Ancient World; which of them were used in Ancient Rus'.
What is the evolution of the simplest visual means and which of them have retained their significance in modern times?
Note how simple means of communication improved the management of society and ensured progress in its development.
Consider whether and where they are used in modern conditions.
Chronicle 10
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Age of the oldest traces of human use of fire |
Historically the first remedy optical communications |
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thousand years ago |
The emergence of artificial methods making fire |
5 ancient methods of its extraction have been studied: scraping (fire plow); sawing out (fire saw); drilling (fire drill with different options); carving, generating fire with compressed air (fire pump) |
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III–II millennium BC e. |
The appearance of polished metal mirrors (bronze, silver), which also became one from visual communications |
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9th century BC e. |
The emergence of the bell as a sound means of communication |
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III century BC e. –XIV century n. e. |
Ptolemy II |
Construction and operation lighthouse on the island of Foros (the second tallest building in the world after the Great Pyramid and the only through a complex reflective system a structure of this type: its light was observed at a distance of 60 km) |
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China Europe |
The advent of firearms which was used and as a means of sound signaling |
Communications units and subunits belong to special troops and are organizationally part of formations and units. They are designed to deploy communication systems and provide command and control of troops in all types of combat activities. They are also entrusted with the tasks of deploying and operating systems and automation equipment at control points, carrying out organizational and technical measures to ensure communication security.
Communication units and units of formations, units and subunits are organizationally divided into battalions, companies, platoons, communications units (crews), as well as FPS stations (units). Their structure and equipment with communications equipment is determined by the staff of the corresponding formations (units).
To ensure command and control of troops in modern combat, they use means of communication: wired, radio, radio relay, tropospheric, space(telecommunications) , as well as mobile and signaling equipment.
Wired means provide high quality communications, ease of organization of communications, greater secrecy of operation compared to radio and radio relay means. Wired channels are not susceptible to intentional enemy radio interference.
However, the great vulnerability of wired assets from all types of enemy weapons, the actions of sabotage and reconnaissance groups, the low speed of work on laying and removing field communication lines, and significant labor costs during operational maintenance make their use difficult.
Radio equipment are used at all levels of management. They are the most important, and sometimes the only means capable of ensuring control of units (units) in the most difficult situations and when commanders and staffs are on the move. Radio equipment allows you to establish communication with objects whose location is unknown, through territory occupied by the enemy, through impassable and contaminated areas. Radio means allow you to transmit combat orders, instructions, reports, commands and signals simultaneously to an unlimited number of correspondents, and establish direct communication through several authorities up and down.
But when using radio equipment, it is necessary to take into account: the possibility of the enemy determining the locations of radio stations operating for transmission; exposure of radio links to enemy radio suppression equipment; the dependence of the quality of radio communications on the conditions of the passage of radio waves and possible interference at the receiving point, the conditions of electromagnetic compatibility of radio-electronic equipment located at one communication center, control point and especially in one object, reducing the communication range when radio equipment operates in motion; influence of high-altitude nuclear explosions on radio communications.
At the tactical control level, radio equipment of the ultra-short wave (VHF) and short wave (HF) ranges is used; VHF radio equipment constitutes the main fleet of radio equipment in the TZU.
Radio relay facilities are capable of providing high-quality multi-channel communication, which is practically little dependent on the time of year and day, weather conditions and atmospheric interference.
But when using them, it is necessary to take into account: the dependence of the communication range on the terrain; short communication range or inability to operate radio relay stations while moving, bulky antenna devices; the ability to intercept transmissions and radio suppression of radio relay lines by the enemy.
Tropospheric and space means Communications at the tactical level can only be used to ensure communication of the formation with higher headquarters and interacting commanders (staffs).
Mobile assets communications are intended to provide courier-postal communications in all types of combat operations and are used for the delivery of military documents, secret and postal items.
By delivering original combat documents to subordinate units (subunits), mobile means ensure absolute reliability of communications. However, it is necessary to take into account the significant time required for the delivery of documents and the possibility of the enemy capturing the delivered combat orders, instructions, reports, etc.
The vehicles used can be helicopters, armored personnel carriers, cars, motorcycles, and in some cases infantry fighting vehicles, tanks, skiers and foot messengers.
Signaling means communications are used to transmit predetermined commands, reports, warning signals, control and interaction, mutual identification, and designation of friendly troops.
Visual (signal flares, smoke bombs, lanterns, flags) and sound (sirens, whistles) means are used as signals.
The role and importance of various communications means are determined by their tactical and technical characteristics and the requirements for ensuring command and control of troops and weapons in specific situational conditions. The main means of communication are those that in a given situation most fully satisfy the need for control. In all cases, means of communication should be used that ensure maximum confidentiality of not only the content of the message, but also the very fact of its transmission.
With the help of technical means of communication, channels and paths of wired, radio, radio relay, tropospheric and space communications are formed. Depending on the terminal facilities and the type of messages transmitted, they are organized types of communication : telephone(incl. auditory radiotelephone), telegraph, data transmission, facsimile, videotelephone. All of them can be either classified or open . With the help of mobile means it is organized courier-postal service.
Telephone communications has high efficiency and brings management closer to the conditions of personal communication. Telephone conversations at the tactical level make up the bulk of the total amount of information and are conducted using classified equipment and SUV documents.
Hearing radiotelephone Communication is organized both with higher headquarters and with subordinate units (subdivisions). It is used to transmit telegrams, radiograms, commands and signals.
Telegraph (secret direct-printing and/or auditory communication) provided in connections for communication with higher headquarters.
Data transfer finds application for information exchange in automated control systems. At the same time, the presence of a set of means for transmitting, receiving and displaying information (display, drawing and graphic apparatus, alphanumeric printing device, etc.) at the automated workstations for officials at control points significantly increases the possibilities for information exchange. The relatively high noise immunity of this type of communication allows the exchange of short data codegrams even in difficult conditions of interference.
Facsimile provides the transmission of black-and-white and color images of combat and formalized documents, diagrams, maps, drawings.
Video telephony combines the advantages of telephone and fax communications, bringing management as close as possible to the conditions of personal communication and allowing you to communicate orders and instructions to subordinates using maps, diagrams, layouts and hear their decisions without leaving your control center.
MEANS OF COMMUNICATION:
DEVELOPMENT,
PROBLEMS,
PROSPECTS
MATERIALS
SCIENTIFIC AND PRACTICAL CONFERENCE
MUNICIPAL EDUCATIONAL INSTITUTION
"NOVOSELITSKA SECONDARY EDUCATION SCHOOL"
NOVGOROD DISTRICT, NOVGOROD REGION
The conference materials contain information from the simplest audio and visual means for transmitting signals and commands to the most modern. The historical path of development and improvement of communications, the role of scientists and practitioners, the latest achievements of physics and technology, and their practical use are shown.
The lesson-conference contributes to the growth of the teacher’s creative potential, the formation of students’ skills in independent work with various sources of information, and allows them to comprehend previously acquired knowledge in a new light, systematize and generalize it. Participation in the conference develops the ability to speak publicly, listen and analyze the messages of your classmates.
The conference materials are designed for creative use and are intended to help teachers prepare and conduct physics lessons.
FROM THE HISTORY OF COMMUNICATIONS
Communications have always played an important role in the life of society. In ancient times, communication was carried out by messengers who transmitted messages orally and then in writing. Signal lights and smoke were among the first to be used. During the day, smoke is clearly visible against the background of clouds, even if the fire itself is not visible, and at night, the flame is visible, especially if it is lit in an elevated place. At first, only pre-agreed signals were transmitted in this way, say, “the enemy is approaching.” Then, by arranging several smokes or lights in a special way, they learned to send entire messages.
Sound signals were used mainly over short distances to gather troops and population. To transmit sound signals, the following were used: a beater (a metal or wooden board), a bell, a drum, a trumpet, a whistle and covers.
The veche bell played a particularly important role in Veliky Novgorod. At his call, Novgorodians gathered at a veche to resolve military and civil matters.
For command and control of troops, banners of various shapes were of no small importance, on which large pieces of various brightly colored fabrics were attached. Military leaders wore distinctive clothing, special headdresses and signs.
In the Middle Ages, flag signaling appeared, which was used in the navy. The shape, color and design of the flags had a specific meaning. One flag could mean a sentence (“The vessel is conducting diving work” or “I require a pilot”), and it, in combination with others, was a letter in a word.
Since the 16th century, the delivery of information using the Yamskaya chase has become widespread in Rus'. Yamskaya tracts were laid to important centers of the state and border cities. In 1516, a Yamskaya hut was created in Moscow to manage the postal service, and in 1550, the Yamskaya order was established - the central institution in Russia in charge of the Yamskaya chase.
In Holland, where there were many windmills, simple messages were transmitted by stopping the wings of the mills in certain positions. This method was developed in optical telegraphy. Towers were erected between cities, which were located at a distance of direct visibility from each other. Each tower had a pair of huge articulated wings with semaphores. The telegraph operator received the message and immediately transmitted it further, moving the wings with levers.
The first optical telegraph was built in 1794 in France, between Paris and Lille. The longest line – 1200 km – operated in the middle of the 19th century. between St. Petersburg and Warsaw. The line had 149 towers. It was served by 1308 people. The signal traveled along the line from end to end in 15 minutes.
In 1832, Russian army officer, physicist and orientalist Pavel Lvovich Schilling invented the world's first electric telegraph. In 1837, Schilling's idea was developed and supplemented by S. Morse. By 1850, the Russian scientist Boris Semenovich Jacobi created a prototype of the world's first telegraph apparatus with letter printing of received messages.
In 1876 (USA) he invented the telephone, and in 1895 a Russian scientist invented the radio. Since the beginning of the twentieth century. Radio communications, radiotelegraph and radiotelephone communications began to be introduced.
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Map of Yamsk tracts of the 16th century. Postal routes of Russia in the 18th century.
COMMUNICATION CLASSIFICATION
Communication can be carried out by filing signals of various physical natures:
Sound;
Visual (light);
Electrical.
According With nature of the signals, used for information exchange, means of transmission (reception) and delivery messages and documents communication can be:
Electrical (telecommunications);
Signal;
Courier-postal.
Depending on the linear means used and the signal propagation medium, communication is divided by gender on the:
Wired communication;
Radio communications;
Radio relay communication;
Tropospheric radio communication;
Ionospheric radio communications;
Meteor radio communication;
Space communications;
Optical communication;
Communication by mobile means.
According to the nature of the messages transmitted and mind communication is divided into;
Telephone;
Telegraph;
Telecode (data transmission);
Facsimile (phototelegraph);
Television;
Video telephone;
Signal;
Courier-postal.
Communication can be done by transmitting information via communication lines:
In clear text;
Coded;
Encrypted (using codes, ciphers) or classified.
Distinguish duplex communication when simultaneous transmission of messages in both directions is ensured and interruption (request) of the correspondent is possible, and simplex communication, when transmission is carried out alternately in both directions.
Communication happens bilateral, in which duplex or simplex information exchange is carried out, or unilateral, if messages or signals are transmitted in one direction without a return response or acknowledgment of the received message.
SIGNAL COMMUNICATION
Signal communication carried out by transmitting messages in the form of predetermined signals using signaling means. In the Navy, signaling communications are used to transmit service information between ships, vessels and raid posts, both in plain text and in signals typed in codes.
For signal communication by means of subject signaling, one-, two- and three-flag sets of Navy signals, as well as a flag semaphore, are usually used. Telegraphic Morse code signs are used to transmit clear text and signal combinations of arches by light-signal devices.
Navy ships and vessels and roadstead posts use the International Code of Signals to negotiate with foreign ships, merchant vessels and foreign coastal posts, especially on issues of ensuring the safety of navigation and the safety of life at sea.
Signaling means, means of signaling visual and audio communication, used to transmit short commands, reports, warnings, designations and mutual identification.
Visual means of communication are divided into: a) means of subject signaling (signal flags, figures, flag semaphore); b) means of light communication and signaling (signal lights, spotlights, signal lights); c) pyrotechnic signaling devices (signal cartridges, lighting and signal cartridges, marine signal torches).
Sound signaling means - sirens, megaphones, whistles, horns, ship bells and fog horns.
Signaling means have been used since the days of the rowing fleet to control ships. They were primitive (drum, lit fire, triangular and rectangular shields). Peter I, the creator of the Russian regular fleet, installed various flags and introduced special signals. 22 ship flags, 42 galley flags and several pennants were installed. With the development of the fleet, the number of signals has also increased. In 1773, the book of signals contained 226 reports, 45 night and 21 fog signals.
In 1779, a Russian mechanic invented a “spotlight” with a candle and developed a special code for transmitting signals. In the 19th – 20th centuries. The means of light communication - lanterns and spotlights - were further developed.
Currently, the Naval Code of Signals flag table contains 32 alphabetic, 10 numeric, and 17 special flags.
PHYSICAL FUNDAMENTALS OF TELECOMMUNICATION
At the end of the twentieth century, widespread telecommunications – transmission of information through electrical signals or electromagnetic waves. Signals travel through communication channels - wires (cables) or wirelessly.
All methods of telecommunication - telephone, telegraph, telefax, Internet, radio and television are similar in structure. At the beginning of the channel there is a device that converts information (sound, image, text, commands) into electrical signals. These signals are then converted into a form suitable for transmission over long distances, amplified to the required power and “sent” to the cable network or radiated into space.
Along the way, the signals are greatly weakened, so intermediate amplifiers are provided. They are often built into cables and placed on repeaters (from the Latin re - a prefix indicating a repeated action, and translator - “carrier”), transmitting signals via terrestrial communication lines or via satellite.
At the other end of the line, the signals enter a receiver with an amplifier, then they are converted into a form convenient for processing and storage, and, finally, they are again converted into sound, image, text, commands.
WIRED COMMUNICATION
Before the advent and development of radio communications, wired communications were considered the main one. By purpose, wired communications are divided into:
Long-distance – for interregional and interdistrict communications;
Internal – for communication in a populated area, in production and office premises;
Service - to manage the operational service on lines and communication centers.
Wired communication lines are often interfaced with radio relay, tropospheric and satellite lines. Wired communication, due to its great vulnerability (natural influences: strong winds, accumulation of snow and ice, lightning strikes or criminal human activity) has disadvantages in application.
TELEGRAPH COMMUNICATION
Telegraph communication is used to transmit alphanumeric information. Auditory telegraph radio communication is the simplest type of communication, which is economical and noise-resistant, but its speed is low. Telegraph direct-printing communication has a higher transmission speed and the ability to document received information.
In 1837, Schilling's idea was developed and supplemented by S. Morse. He proposed a telegraph alphabet and a simpler telegraph apparatus. In 1884, the American inventor Morse commissioned the first writing telegraph line in the United States between Washington and Baltimore, 63 km long. Supported by other scientists and entrepreneurs, Morse achieved significant distribution of his devices not only in America, but also in most European countries.
By 1850, Russian scientist Boris Semenovich Jacobi
(1801 - 1874) created a prototype of the world's first telegraph apparatus with letter printing of received messages.
The operating principle of a writing electromagnetic telegraph apparatus is as follows. Under the influence of current pulses coming from the line, the armature of the receiving electromagnet was attracted, and in the absence of current, it was repelled. A pencil was attached to the end of the anchor. In front of him, a matte porcelain or earthenware plate moved along guides using a clock mechanism.
When the electromagnet was operating, a wavy line was recorded on the plate, the zigzags of which corresponded to certain signs. A simple key was used as a transmitter, closing and opening an electrical circuit.
In 1841, Jacobi built the first electric telegraph line in Russia between the Winter Palace and the General Headquarters in St. Petersburg, and two years later a new line to the palace in Tsarskoe Selo. Telegraph lines consisted of insulated copper wires buried in the ground.
During the construction of the St. Petersburg-Moscow railway, the government insisted on laying an underground telegraph line along it. Jacobi proposed building an overhead line on wooden poles, arguing that the reliability of communications over such a long distance could not be guaranteed. As one might expect, this line, built in 1852, did not last even two years due to imperfect insulation and was replaced by an overhead line.
The academician carried out important work on electrical machines, electrical telegraphs, mine electrical engineering, electrochemistry and electrical measurements. He discovered a new method of electroplating.
The essence of telegraph communication is the representation of a finite number of symbols of an alphanumeric message in the transmitter of a telegraph apparatus by a corresponding number of different combinations of elementary signals. Each such combination, called a code combination, corresponds to a letter or number.
Transmission of code combinations is usually carried out by binary alternating current signals, most often modulated by frequency. Upon reception, the electrical signals are converted back into characters and these characters are registered on paper in accordance with the accepted code combinations.
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Telegraph communication is characterized by reliability, speed of telegraphy (transmission), reliability and secrecy of transmitted information. Telegraph communications are developing in the direction of further improving equipment, automating the processes of transmitting and receiving information.
TELEPHONE COMMUNICATIONS
Telephone communication is intended for conducting oral conversations between people (personal or business). When managing complex air defense systems, railway transport, oil and gas pipelines, operational telephone communication is used, which ensures the exchange of information between the central control point and controlled objects located at a distance of up to several thousand km. It is possible to record messages on audio recording devices.
The telephone was invented by an American on February 14, 1876. Structurally, Bell's telephone was a tube with a magnet inside. On its pole pieces there is a coil with a large number of turns of insulated wire. A metal membrane is located opposite the pole pieces.
Bell's telephone receiver was used to transmit and receive speech sounds. The call to the subscriber was made through the same handset using a whistle. The range of the phone did not exceed 500 m.
A miniature color television camera equipped with a micro-bulb turns into a medical probe. By inserting it into the stomach or esophagus, the doctor examines what previously could only be seen during surgery.
Modern television equipment allows you to control complex and hazardous production. The operator-dispatcher monitors several technological processes simultaneously on the monitor screen. The operator-dispatcher of the road safety service solves a similar problem, monitoring traffic flows on roads and intersections on the monitor screen.
Television is widely used for surveillance, reconnaissance, control, communications, command and control, in weapon guidance systems, navigation, astro-orientation and astro-correction, for monitoring underwater and space objects.
In the missile forces, television makes it possible to monitor preparations for launch and launch of missiles, monitoring the condition of units and components in flight.
In the navy, television provides control and surveillance of the surface situation, overview of premises, equipment and personnel actions, search and detection of sunken objects, bottom mines, and rescue operations.
Small-sized television cameras can be delivered to the reconnaissance area using artillery shells, unmanned aircraft controlled by radio.
Television has found wide application in simulators.
Television systems, working in conjunction with radar and direction-finding equipment, are used to provide air traffic control services at airports, flights in adverse weather conditions and blind landings of aircraft.
The use of television is limited by insufficient range, dependence on weather and lighting conditions, and low noise immunity.
Television development trends include expanding the range of spectral sensitivity, introducing color and volumetric television, reducing the weight and dimensions of equipment.
VIDEO PHONE COMMUNICATION
Videotelephony - a combination of telephone communication and slow-motion television (with a small number of scan lines) - can be carried out over telephone channels. It allows you to see your interlocutor and show simple still images.
FELDJEGERSKO – POSTAL SERVICES
Delivery of documents, periodicals, parcels and personal correspondence is carried out using couriers and mobile communications equipment: airplanes, helicopters, cars, armored personnel carriers, motorcycles, boats, etc.
CONNECTION QUALITY
The quality of communication is determined by the totality of its interconnected basic properties (characteristics).
Timeliness communications– its ability to ensure the transmission and delivery of messages or negotiations at a given time is determined by the deployment time of nodes and communication lines, the speed of establishing communication with the correspondent, and the speed of information transfer.
Communication reliability– its ability to operate reliably (stablely) for a certain period of time with the reliability, secrecy and speed specified for given operating conditions. A significant impact on the reliability of communication is exerted by the noise immunity of the communication system, lines, channels, which characterizes their ability to function under conditions of exposure to all types of interference.
Reliability of communication– its ability to ensure the reception of transmitted messages with a given accuracy, which is estimated by the loss of reliability, that is, the ratio of the number of characters received with error to the total number of transmitted ones.
In conventional communication lines, the loss of reliability is at best 10-3 - 10-4, so they use additional technical devices to detect and correct errors. In automated control systems in developed countries, the reliability standard is 10-7 – 10-9.
Communication secrecy characterized by the secrecy of the fact of communication, the degree to which distinctive features of communication are revealed, and the secrecy of the content of the transmitted information. The secrecy of the content of transmitted information is ensured through the use of classification, encryption, and encoding equipment for transmitted messages.
PROSPECTS FOR COMMUNICATION DEVELOPMENT
Currently, all types and types of communications and the corresponding technical means are being improved. In radio relay communications, new sections of the ultra-high frequency range are used. In tropospheric communications, measures are taken against communication disruptions due to changes in the state of the troposphere. Space communications are being improved on the basis of “stationary” relay satellites with multiple access equipment. Optical (laser) communication is being developed and practically used, primarily for transmitting large amounts of information in real time between satellites and spacecraft.
Much attention is paid to standardization and unification of blocks, components and elements of equipment for various purposes in order to create unified communication systems.
One of the main directions for improving communication systems in developed countries is to ensure the transmission of all types of information (telephone, telegraph, facsimile, computer data, etc.) in converted discrete-pulse (digital) form. Digital communication systems have great advantages in creating global communication systems.
LITERATURE
1. Computer science. Encyclopedia for children. Volume 22. M., “Avanta+”. 2003.
2. At the origins of television. Newspaper "Physics", No. 16, 2000.
3. Craig A., Rosni K. Science. Encyclopedia. M., "Rosman". 1994.
4. Kyandskaya-, On the issue of the world’s first radiogram. Newspaper "Physics", No. 12, 2001.
5. Morozov invented, and for which G. Marconi received a patent. Newspaper "Physics", No. 16, 2002.
6. MS - DOS - no question! Editorial and Publishing Center "Tok". Smolensk 1993.
7. Reid S., Farah P. History of discoveries. M., "Rosman". 1995.
8. Soviet military encyclopedia. M., Military Publishing House of the Ministry of Defense. 1980.
9. Technique. Encyclopedia for children. Volume 14. M., “Avanta+”. 1999.
10. Turov military communications. Volume 1,2,3. M., Military Publishing House. 1991.
11. Wilkinson F., Pollard M. Scientists who changed the world. M., “The Word”. 1994.
12. Urvalov of television equipment. (ABOUT). Newspaper "Physics", No. 26, 2000.
13. Urvalov electronic television. Newspaper "Physics", No. 4, 2002.
14. Fedotov schemes by O. Lodge, G. Marconi. Newspaper "Physics", No. 4, 2001.
15. Physics. Encyclopedia for children. Volume 16. M., “Avanta+”. 2000.
16. Hafkemeyer H. Internet. Journey through the worldwide computer network. M., “The Word”. 1998.
17. At the origins of radar in the USSR. M., “Soviet Radio”. 1977.
18. Schmenk A., Wetjen A., Käthe R. Multimedia and virtual worlds. M., “The Word”. 1997.
Preface…2
From the history of communications... 3
Communication classification ... 5
Signal communication... 6
Physical foundations of telecommunications ... 7
Wired communication... 7
Telegraph communication ... 8
Telephone connection ... 10
Telecode communication... 12
Internet... 12
Optical (laser) communication ... 14
Fax communication... 14
Radio communication ... 15
Radio relay communication... 17
Tropospheric communication ... 17
Ionospheric radio communication ... 17
Meteor radio communication ... 17
Space communications ... 18
Radar… 18
Television communication ... 21
Videotelephony…24
Courier-postal service… 24
Communication quality ... 25
Prospects for the development of communications ... 25
Literature ... 26
Responsible for release:
Computer layout: Press Boris
ELECTRONIC COMMUNICATIONS
a technique for transmitting information from one place to another in the form of electrical signals sent through wires, cables, fiber optic lines, or without any guide lines at all. Directed transmission by wire is usually carried out from one specific point to another, as in telephony or telegraphy. Undirectional transmission, on the other hand, is typically used to transmit information from one point to many other points scattered in space, i.e. for broadcast purposes. An example of non-directional transmission is radio broadcasting. Wire transmission can be thought of as the flow of electrical current through a wire, which is interrupted or altered in some way, from a transmitter located at one point in the network. It is an interruption or change in current detected by a receiver at another point on the network and represents a signal, or piece of information, sent by the transmitter. The transmission of information through radio or optical (light) waves is electromagnetic radiation that can propagate without the need of any medium, i.e. capable of spreading in a vacuum. Such transmission occurs as a result of oscillations of 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 vibration frequency, with radio waves corresponding to the low-frequency end of the spectrum, and gamma rays to the high-frequency end.
see also ELECTROMAGNETIC RADIATION . 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 from about 1 to 30,000 MHz. In this range, AM radio broadcasts are conducted at frequencies from 0.5 to 1.5 MHz, and FM and television broadcasts are carried out in a much wider frequency range, the middle of which is at 100 MHz. Microwave signals, including those sent to and received from communications satellites, range from 4,000 to 14,000 MHz and even higher. Generally speaking, any signal requires a certain band or range of frequencies; Moreover, the more complex the signal, the wider the required frequency band. For example, a television signal, due to its much greater complexity, requires a bandwidth approximately 600 times greater than that of a speech signal. The entire radio frequency spectrum used allows it to accommodate 10 million voice or about 10,000 television channels. This spectrum is shared among broadcast stations, emergency services, aviation, ships, mobile telephony, military and other users.
A revolution in communications. In recent decades, electronic communications have developed so rapidly that the words “communications revolution” do not seem like an exaggeration. The basis for many innovations was the rapid progress of electronic equipment and technology. In the early 1950s, a device called a transistor was developed. This miniature electronic component, made of semiconductor materials, is used to amplify or control electrical current. Because transistors are smaller and more durable than vacuum tubes, they replaced tubes in radios and became the basis of computers.
see also ELECTRIC VACUUM AND GAS DISCHARGE DEVICES; TRANSISTOR.
In the late 1960s, computer technology began to replace transistor circuits with 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 to produce hundreds of thousands of transistors at once in one process. This technique, called large-scale integrated circuit (LSI) technology, allows multiple ICs to be housed in one small device.
see also INTEGRATED CIRCUIT . Each stage of electronics development 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, communications satellites, direct dial telephones, video phones, transistor radios and cable television has led to a complete overhaul of the traditional classification of communication methods. Nowadays, transmission over wires is practically no longer identified with direct address communication, and wireless transmission with radio broadcasting. Probably the most powerful influence on the development of communications technology was the significant increase in the capacity of communications, both over the air and by wire. This increased capacity is used for the ever-increasing global television, telephony and digital information traffic.
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 in the same way that a radio transmitter serves as a source of lower frequency waves (radio waves). Since the frequency range of light waves (approximately from 5-108 to 109 MHz) is many times wider than the frequency range of radio waves, a light beam can transmit enormous amounts of information. This part of the electromagnetic spectrum is wide enough to accommodate 80 million TV channels or support 50 billion simultaneous telephone conversations. In the communication technology used in practice, laser signals of a slightly lower frequency (infrared radiation) are transmitted from point to point via fiber-optic lines characterized by low losses. An optical cable contains from 10 to 100 or more optical fibers, each of which can transmit a television signal or operate many hundreds of telephone channels. Lasers are also used to transmit signals between military satellites. Lasers used in communications are tiny semiconductor devices similar to the light-emitting diodes (LEDs) used in the digital displays of pocket calculators and wristwatches. see also LASER ; QUANTUM GENERATORS AND AMPLIFIERS.
Communications satellites. The first communications satellites, placed in low-Earth orbits in the early 1960s, carried passive equipment and served only as signal repeaters.
see also COMMUNICATIONS SATELLITE. Modern communications satellites are typically launched into 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 oceans to entire continents and support the operation of more than tens of thousands of telephone channels.
Cables. During World War I, communications technicians developed a method of using pairs of wires to transmit multiple telephone conversations simultaneously. This method, called frequency division multiplexing, is based on the ability to transmit a wide range of audio frequencies over a pair of wires. In this case, the signals from each of several transmitters are separated in frequency (using modulation) and the resulting higher-frequency combined signal is transmitted to the receiving terminal, where it is divided into component signals through demodulation. A jacketed telephone cable may contain tens to hundreds of twisted wire pairs, each capable of supporting up to 24 telephone channels. 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 the neighboring 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 second conductor tube. The center conductor and tube are electrically isolated from each other.
TASI. Time-Speed Speech Interpolation (TASI) is a technique that doubles the capacity of transoceanic telephone cables by exploiting natural pauses in conversations. The two-way communication channel is idle for approximately 60% of the time during pauses in the conversation, as well as while the user is working to receive. 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 begins to speak, and disconnects him immediately after silence, providing the channel in pauses to other subscribers.
Pulse code modulation. This method of transmitting signals using 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 the signal. These pulses are sent to the receiving station in place of the original signals. One of the advantages of PCM is due to the fact that discrete electronic pulses of constant amplitude can be easily distinguished from random interference of arbitrary amplitude (electrostatic origin), which is present to one degree or another in any transmission medium. Such pulses can be transmitted essentially without interference from extraneous noise since they can be easily separated. PCM is used for a wide variety of signals. Telegraph and facsimile messages, as well as other data that were previously sent over telephone lines by other methods, can be transmitted much more efficiently in pulsed form. The traffic of such non-speech signals is continuously increasing; There are also systems that allow the transmission of mixed signals of speech, data and video information.
Electronic switching. Another innovation that has led to increased efficiency in telephone communication is electronic switching. The modern microcircuits described above have made it possible to use electronic switches in PBX instead of mechanical ones, which has increased the speed and reliability of calls. New switching systems are digital systems that use fast, compact LSIs to switch data, PCM or video signals in digital form. In addition to being well suited for a variety of telephony applications, electronic switching allows for a number of innovations. These include: automatic call transfer to another number when the subscriber’s number is busy; speed dialing, in which the subscriber dials only one or two digits to connect to frequently called numbers; Call signals that notify the user that another subscriber is trying to connect to him.
Telephones and computers. The telephone of the future will be used not only for ordinary communications. Telephones with built-in miniature, low-cost logic circuits will be capable of performing complex electronic functions. With the help of a PBX, such a phone can become an individual computer. By pressing the keys on his telephone, the user will be able to enter data he wants to store, process information, query data from some central file, or perform calculations.
Videophone. New electronics make it possible to supplement audio information transmitted over the telephone with images. Video transfers between conference rooms located in several cities are used to avoid the need for conference participants to travel. Video broadcasts have begun to be widely used for training - lectures are transmitted from one audience to another (remote) and recorded on video tape for use for the same purposes.
Cable television systems. Although laser radiation and millimeter waves can be used for broadcasting, limitations due to atmospheric absorption and various other types of interference can only be overcome at great cost. Cable systems are therefore increasingly being used to find ways to expand broadcasting without the limitations of electromagnetic emissions. Cable television requires laying cables from transmitting to receiving stations located, for example, in homes. A radio listener or cable TV viewer does not experience inconvenience from fading, ghosting and other interference. In addition, due to the fact that the number of channels transmitted by cable is practically unlimited (whereas a typical TV broadcast station broadcasts only one program at a time), the viewer has 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 operating 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.
Computer as an intelligent assistant. Computer scientists believe that eventually people will be able to communicate their ideas more effectively using computers than through direct conversation. Typically, the purpose of a conversation is to exchange, compare, and critically discuss ideas already formed in the minds of the participants in the conversation. Ideas are mainly expressed in words, but if the subject matter is complex or technical, then graphics, photographs and calculations must be used. Conversation does not always lead to full understanding because the concepts being presented may not be easy to express in words; they often contain data and associations that are interconnected in such a complex way that even the speaker finds it difficult to fully understand and express them. The listener is unable to investigate the speaker's way of thinking and must rely on the information that he communicates, and with a degree of inadequacy that is difficult to assess. The computer, according to cyberneticists, provides the participant in a 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, can collate 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 clearly enough when the interlocutor explained this idea, then the output of the computer can give a general idea of the speaker's way of thinking. In this way, the speaker's basic information is made available to the listener. In addition, the student may need a computer to sort through data to identify facts relevant to the problem or concept being discussed. Discussions can then arise 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 arise to a degree and at a level that could not be achieved without the use of computers. Experiments carried out in this direction have yielded encouraging results.
see also
ARTIFICIAL INTELLIGENCE;
OFFICE EQUIPMENT AND OFFICE EQUIPMENT;
TELEPHONE ;
COMPUTER ;
INFORMATION ACCUMULATION AND SEARCH;
RADIO AND TELEVISION;
FIBER OPTICS ;
COMMUNICATIONS SATELLITE;
TELEMETRY ;
SEMICONDUCTOR ELECTRONIC DEVICES.
LITERATURE
Ignatov V.A. Theory of information and signal transmission. M., 1979 Levin L.S., Plotkin M.A. Digital information transmission systems. M., 1982 Enderline R. Microelectronics for everyone. M., 1989 Apokin I., Maistrov L. History of computer technology. M., 1990
Collier's Encyclopedia. - Open Society. 2000 .
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