Development of modern means of communication
Communication means - hardware and software used for the formation, reception, processing, storage, transmission, delivery of telecommunication messages or postal items, as well as other hardware and software used in the provision of communication services or ensuring the operation of communication networks.
types of communication Wired (telephone, telegraph, etc.) Wireless, which, in turn, distinguish: radio (omnidirectional, narrowly directed, cellular and other radio systems), radio relay and space (satellite) devices, systems and complexes.
Communication means. The first is the emergence of oral speech. Scientists have identified five powerful impulses that accelerated the development of mankind, which culture received during its existence:
The second is the invention of writing, which allowed a person to enter into communication with other people who are not in direct contact with him.
The third is the emergence and spread of book printing.
Fourth - the emergence of electronic mass communication, which provided an opportunity for everyone to become a direct witness and participant in the historical and cultural process taking place all over the world. Radio Television
Fifth, according to many experts, - the emergence and development of the Internet as a new means of communication, providing ample opportunities in the forms and methods of receiving and transmitting information, as well as the implementation of many other functions.
Stages of development of communication facilities Creation of an optical telegraph - a device for transmitting information over long distances using light signals. This system was invented by the Frenchman Claude Chappe.
Wire communication. The first electric telegraph was created in 1837 by English inventors: William Cook Charles Watsone
Late model of the Cook and Wheatstone telegraph. The signals triggered arrows on the receiver, which pointed to different letters and thus conveyed the message.
Morse Code In 1843, the American artist Samuel Morse invented a new telegraph code that replaced the Cook and Wheatstone code. He designed dots and dashes for each letter.
And Charles Whetstone created a system in which an operator, using Morse code, typed messages on a long paper tape that entered the telegraph apparatus. At the other end of the wire, the recorder was stuffing the received message onto another paper tape. Subsequently, the recorder was replaced by a signaling device that converted dots and dashes into long and short sounds. Operators listened to the messages and recorded their translation.
The invention of the first telephone. Alexander Graham Bell (1847-1922), together with Thomas Watson (1854-1934), designed a device consisting of a transmitter (microphone) and a receiver (speaker). Microphone and speaker were arranged the same In the microphone, the speaker's voice made the membrane vibrate, causing the electric current to oscillate ... In the dynamics, the current flowed to the membrane, causing it to vibrate and reproduce the sounds of a human voice. The first telephone conversation took place on March 10, 1876.
The invention of the radio. Radio creator Alexander Stepanovich Popov (1859-1906). On May 7, 1895, Popov demonstrated the radio receiver he invented at a meeting of the physics department of the Russian Physicochemical Society. A type of wireless communication in which radio waves are used as a signal carrier, freely propagating in space.
Satellite connection. Satellites are unmanned spacecraft that orbit around the Earth. They can transmit telephone conversations and television signals anywhere in the world. They also transmit weather and navigation information. In 1957, the USSR launched Sputnik 1, the world's first artificial Earth satellite.
In 1960, the Kurier and Echo satellites were launched in the United States. They transmitted the first telephone conversations between the US and Europe. In 1962, Telstar, the first television satellite, entered orbit in the United States.
Fiber optic communication lines. Fiber-optic communication lines (FOCL) are currently considered the most advanced physical medium for transmitting information. Data transmission in optical fiber is based on the effect of total internal reflection. Thus, the optical signal transmitted by the laser from one side is received from the other, significantly distant side. To date, a huge number of backbone fiber-optic rings, intracity and even intraoffice, have been built and are under construction.
Laser communication system Quite an interesting solution for high-quality and fast network communication was developed by the German company Laser2000. The two presented models look like the most common video cameras and are intended for communication between offices, inside offices and along the corridors. Simply put, instead of laying an optical cable, you just need to install inventions from the Laser2000. However, in reality, these are not video cameras, but two transmitters that communicate with each other using laser radiation. Recall that a laser, unlike ordinary light, for example, lamp, is characterized by monochromaticity and coherence, that is, the laser beams always have the same wavelength and are scattered little.
Links to sources of information and images: www.digimedia.ru/articles/svyaz/setevye-tehnologii/istoriya/faks-istoriya-ofisnogo-vorchuna/ http://ru.wikipedia.org/wiki/%D0%9F%D0% BE% D0% BF% D0% BE% D0% B2, _% D0% 90% D0% BB% D0% B5% D0% BA% D1% 81% D0% B0% D0% BD% D0% B4% D1% 80_% D0% A1% D1% 82% D0% B5% D0% BF% D0% B0% D0% BD% D0% BE% D0% B2% D0% B8% D1% 87 http://geniusweb.ru/? feed \u003d rss2 ru.wikipedia.org/wiki/ Radio http://www.5ka.ru/88/19722/1.html
Slide 2
Answer the questions
What is called an infrastructure complex? What does the infrastructure complex have in common? Which industries are part of the infrastructure complex? What is the difference between the production and non-production areas of the complex? To which area of \u200b\u200bthe complex can the topic of our lesson be attributed?
Slide 3
Communication is a branch of the economy that provides reception and transmission of information.
What do you think the postal service does?
Slide 4
Postal communication
In the old days in Russia, communication between the capital and peripheral cities, as well as between the troops participating in hostilities, was carried out with the help of special messengers-horsemen. This method was improved by the Tatars, creating on the roads at a distance of 30 - 40 km. special stations ("pits"), where the coachmen could rest and change horses. In the 17th century Moscow was connected by such "pits" with Novgorod, Pskov, Smolensk, Arkhangelsk and Nizhny Novgorod. The first regular post office for sending state papers and letters of merchants was established in 1666. Under Peter I, maximum terms (norms) for the delivery of correspondence were established. Under Catherine II, a kind of tax was introduced for letters and parcels, depending on the weight and distance of their transportation. In the 19th century, post offices were transferred to the jurisdiction of the Ministry of the Interior. The main function of the post office consisted of sending ordinary and registered letters, postcards (introduced in 1872) and parcels. Small amounts of money, including copper, silver and gold coins, could be sent in special packages and leather bags. They, like valuable parcels, were insured. Since 1897, they began to accept postal and then telegraphic money orders. The Post also took upon itself the delivery of periodicals, charging for this, depending on the frequency of publication of newspapers or magazines, from 6 to 18% of the total cost of the subscription. Electric traditional communication The following data testifies to the dynamic development of postal communication. If in 1897. In Russia, there were only 2.1 thousand postal and telegraph institutions, then in 1913 their number increased to 11 thousand, and the total length of postal routes increased to 261 thousand km.
Slide 5
Telephone communications
The telephone first appeared in Russia in 1880. Initially, the government planned to establish a state monopoly on telephone communications. However, due to the high cost of building and operating telephone exchanges, private capital began to be attracted to their creation. According to the signed contracts, telephone exchanges and lines built at the expense of private companies, after 20 years of operation, passed into state ownership. By the beginning of the 20th century, 77 state and 11 private telephone exchanges operated in Russia. Telephone charges in the public sector were half that of the private sector. In total, in 1913, 300 thousand telephones were installed in Russian cities.
Slide 6
Features of telephone communication
The main indicator of the development of the public telecommunication services market is telephone density (TP), that is, the number of telephones per 100 inhabitants, which is directly correlated with the GDP per capita indicator. According to official statistics, at the end of the 90s, the telephone park in Russia totaled more than 31 million phones, that is, there were 21 telephones per 100 Russians, while the same number of residents of the United States and Western Europe had from 60 to 70 telephones. ... In Russia, at the beginning of the third millennium, 54 thousand settlements were not provided with telephones, there were 6 million people on the waiting list and about 50 million potential owners of telephones. Tariffs for local telephone communication for the population were lower than the actual cost
Slide 7
Radio Television Communication
At the end of the 19th century, radio communication appeared - the wireless transmission of electrical signals over long distances using radio waves (electromagnetic waves with a frequency in the range of 105-1012 Hz). Later, powerful transmitters and sensitive receivers appeared, their sizes were reduced, and the parameters improved. Inventions of the phototelegraph and television communication were significant achievements in the development of communication facilities. Video signals are transmitted using these communication media. For the implementation of television communications, two transmitters are needed: one for audio signals, the other for video signals. The next step in improving television communications was the invention of color television.
Slide 8
Telegraph communication
The first telegraph line appeared in Russia in 1835. It connected St. Petersburg with Kronstadt and was intended for the needs of the military department. Four years later, the construction of the second line was completed, which connected the northern capital with Warsaw. Since the mid-1950s, where the railways were built, the German firm Siemens has been laying a telegraph equipped with new electromagnetic technology. By the beginning of the 20th century, the length of state telegraph lines was 127 thousand versts. By that time, underwater telegraph cables had been laid connecting Russia with Denmark and Sweden. Russian telegraph lines were connected to telegraph lines in China and Japan. If in 1897 14 million internal telegrams were sent, then in 1912 more than 36 million were sent.
Slide 9
Telegram - a message sent by telegraph, one of the first types of communication using electrical transmission of information. Telegrams are usually transmitted by wire using Morse code. Telegrams are printed on paper tape, which is then pasted onto a sheet of paper for ease of reading. Telegraph (from the Greek. Tele - "far" + grapho - "I write") - in the modern sense - a means for transmitting a signal over wires or other telecommunication channels. Electrical new connection
Slide 10
Slide 11
Satellite connection
Satellite communication is one of the types of radio communication based on the use of artificial earth satellites as repeaters. Satellite communication is carried out between earth stations, which can be both fixed and mobile. The subscribers of the network in the regions will receive the following services via the satellite communication channel: fax, telephone, Internet, radio and TV programs.
Slide 12
Digital communication is a field of technology related to the transmission of digital data over a distance.
Slide 13
Telex communication
By 1930, the design of a start-stop telegraph apparatus was created, equipped with a disk-type telephone dialer (teletype). This type of telegraph apparatus, among other things, made it possible to personify the subscribers of the telegraph network and to carry out their fast connection.
Slide 14
Electronic mail (English E-mail or email, abbreviated from electronic mail) is a method of transmitting information in computer networks, widely used on the Internet.
The main feature of e-mail: information is sent to the recipient not directly, but through an intermediate link - an electronic mailbox, which is a place on the server where the message is stored until the recipient requests it.
Slide 15
Cellular communication is one of the types of mobile radio communication, which is based on the cellular network.
A cell phone is a mobile communication device that uses a combination of radio transmission and traditional telephone switching to carry out telephone communications in an area (coverage area) consisting of "cells" surrounding the base stations of a cellular network. Currently, cellular communication is the most widespread of all types of mobile communication, therefore, a cell phone is usually called a mobile phone, although mobile phones, in addition to cellular phones, are also radio phones, satellite phones and trunking devices. Cellular penetration in Russia was 87%, and in Moscow and St. Petersburg it has already reached 100%.
Slide 17
The number of Russians with mobile phones at their disposal has grown from 40% in mid-2005 to 52% this year. More than half of Russians already use telephones at home - 55% (over the year their number has grown by one percent). According to sociologists, the number of Russians who have a computer in their homes is also growing - now 20% of respondents have it (15% a year ago). According to the study, now 19% of Russians (against 17% a year ago) use a personal computer daily or several times a week at home, at work and elsewhere, 5% - about once a week (3%), never use a computer - 73% (last year - 76%).
View all slides
In the modern world, there are various means of communication that are constantly developing and improving. Even such a traditional form of communication as postal communication (delivery of messages in writing) has undergone significant changes. This information is delivered by rail and airplane to replace the old postage carriages.
With the development of science and technology, new types of communication appear. So in the 19th century, the wire telegraph appeared, through which information was transmitted using Morse code, and then the telegraph was invented, in which dots and dashes were replaced by letters. But this type of communication required long transmission lines, cable laying under ground and water, in which information was transmitted by means of electrical signals. The need for transmission lines also remained in the transmission of information by means of a telephone.
At the end of the 19th century, radio communication appeared - the wireless transmission of electrical signals over long distances using radio waves (electromagnetic waves with a frequency in the Hz range). But for the development of this type of communication, it was necessary to increase its range, and for this it was necessary to increase the power of transmitters and the sensitivity of receivers receiving a weak radio signal. These problems were gradually solved with the advent of new inventions - vacuum tubes in 1913, and after the Second World War they began to be replaced by semiconductor integrated circuits. Powerful transmitters and sensitive receivers appeared, their size decreased and their parameters improved. But the problem remained - how to get the radio waves to circumnavigate the globe.
And the property of electromagnetic waves was used to be partially reflected at the interface between two media (waves were weakly reflected from the surface of the dielectric, and almost without loss from the conducting surface). The layer of the earth's ionosphere, the upper layer of the atmosphere consisting of ionized gases, began to be used as such a reflective surface.
Back in 1902, the English mathematician Oliver Heaviside and the American electrical engineer Arthur Edwin Kennelly predicted almost simultaneously that there is an ionized layer of air above the Earth - a natural mirror that reflects electromagnetic waves. This layer was named the ionosphere. The ionosphere of the Earth was supposed to allow increasing the range of propagation of radio waves to distances exceeding the line of sight. Experimentally, this assumption was proven in RF pulses were transmitted vertically upward and returned signals were received. Measurements of the time between sending and receiving pulses made it possible to determine the height and number of reflection layers.
After being reflected from the ionosphere, short waves return to the Earth, leaving hundreds of kilometers of the "dead zone" under them. Having traveled to the ionosphere and back, the wave does not "calm down", but is reflected from the Earth's surface and again rushes to the ionosphere, where it is reflected again, etc. Thus, repeatedly reflecting, a radio wave can circumnavigate the globe several times. It was found that the reflection height depends primarily on the wavelength. The shorter the wave, the higher the height it is reflected and, therefore, the larger the "dead zone". This dependence is valid only for the short-wavelength part of the spectrum (up to about 25-30 MHz). For shorter wavelengths, the ionosphere is transparent. Waves penetrate her and go into outer space. It can be seen from the figure that the reflection depends not only on the frequency, but also on the time of day. This is due to the fact that the ionosphere is ionized by solar radiation and gradually loses its reflectivity with the onset of darkness. The degree of ionization also depends on solar activity, which changes throughout the year and from year to year in a seven-year cycle.
This layer perfectly reflects radio waves from a length of meters. Repeatedly and alternately reflected from the ion of the sphere and the surface of the earth, short radio waves go around the globe, transmitting information to the most distant parts of the planet. After the telephone was invented and methods of long-distance radio communication were found, the desire to combine these two achievements naturally arose. It was necessary to solve the problem of transmitting low-frequency electrical vibrations created by vibration of the membrane of a telephone receiver under the influence of a human voice. And it was solved by mixing these low frequency vibrations with the high frequency electrical vibrations of a radio transmitter. The shape of the high-frequency radio waves changed in strict accordance with the sounds produced by the low-frequency electrical vibrations. Sound vibrations began to spread with the speed of radio waves. In a radio receiver, the mixed radio signal was separated and low-frequency sound vibrations reproduced the transmitted sounds.
Inventions of the phototelegraph and television communication were significant achievements in the development of communication facilities. Video signals are transmitted using these communication media. Now, with the help of a phototelegraph, the text of newspapers and various information is transmitted over great distances. The number of television channels, which occupy the region of ultra-high radio frequencies from 50 to 900 MHz, is constantly growing. Each television channel is about 6 MHz wide. Within the limits of the operating frequency of the channel, 3 signals are transmitted: sound, transmitted by the frequency modulation method; a video signal transmitted by the amplitude modulation method; synchronization signal.
Naturally, for the implementation of television communication, two transmitters are needed: one for audio signals, the other for video signals. The next step in improving television communications was the invention of color television. But modern requirements for communication facilities constantly require their further improvement, now the introduction of digital systems for transmitting information, images, sound is starting, which in the future will replace the current analog television. New generation television receivers allow receiving digital and analogue broadcasts. The usual screens of TVs and displays are being replaced by liquid crystal ones. Liquid crystal silicon displays using thin film technology can dramatically reduce power consumption by eliminating the need for backlighting. Sharp has already created televisions with new capabilities, Internet access and e-mail. At the turn of the century, the use of digital systems, liquid crystals, optical fibers in communication means allows solving several extremely important problems for a person at once: reducing energy consumption, decreasing (or, conversely, increasing) the size of equipment, multifunctionality, and accelerating the exchange of information.
With the help of such communication satellites, a variety of information is transmitted: from radio and television broadcasts to top-secret military information. Recently, a communications satellite was launched to carry out financial transactions by Russian banks, which will greatly speed up the passage of payments in such a vast territory as our country. Whole satellite communication networks are being created, which will make it extremely easy for Russian regional users to access world information flows. The subscribers of the network in the regions will receive the following services via the satellite communication channel: fax, telephone, Internet, radio and TV programs.
Stages of development of communication facilities English scientist James Maxwell in 1864 theoretically predicted the existence of electromagnetic waves. English scientist James Maxwell in 1864 theoretically predicted the existence of electromagnetic waves, experimentally discovered by Heinrich Hertz at the University of Berlin, Heinrich Hertz discovered experimentally at the University of Berlin. May 7, 1895 A.S. Popov invented the radio. May 7, 1895 A.S. Popov invented the radio. In 1901, the Italian engineer G. Marconi for the first time carried out radio communications across the Atlantic Ocean. In 1901, the Italian engineer G. Marconi for the first time carried out radio communications across the Atlantic Ocean. B.L. Rosing May 9, 1911 electronic television. B.L. Rosing May 9, 1911 electronic television. 30 years V.K. Zvorykin invented the first transmitting tube - the iconoscope. 30 years V.K. Zvorykin invented the first transmitting tube - the iconoscope.
Communication is the most important link in the country's economic system, the way people communicate, the satisfaction of their production, spiritual, cultural and social needs is the most important link in the country's economic system, the way people communicate, the satisfaction of their production, spiritual, cultural and social needs
The main directions of development of communication facilities Radio communication Radio communication Telephone communication Telephone communication Television communication Telegraph communication Cellular communication Internet Internet Space communication Space communication Phototelegraph (Fax) Phototelegraph (Fax) Video telephone communication Video telephone communication Telegraph communication Telegraph communication
Space communications SPACE COMMUNICATIONS, radio communications or optical (laser) communications between ground receiving and transmitting stations and spacecraft, between several ground stations, mainly through communications satellites or passive repeaters (eg, a belt of needles), between several spacecraft. SPACE COMMUNICATION, radio communication or optical (laser) communication between ground receiving and transmitting stations and spacecraft, between several ground stations, mainly through communication satellites or passive repeaters (e.g., a belt of needles), between several spacecraft.
Phototelegraph Phototelegraph, the common abbreviation for facsimile communication (phototelegraph communication). A type of communication for transmitting and receiving images printed on paper (manuscripts, tables, drawings, drawings, etc.). A type of communication for transmitting and receiving images printed on paper (manuscripts, tables, drawings, drawings, etc.). A device that makes such a connection. A device that makes such a connection.
The first phototelegraph At the beginning of the century, the German physicist Korn created a phototelegraph, which does not fundamentally differ from modern drum scanners. (The figure on the right shows a diagram of Korn's telegraph and a portrait of the inventor, scanned and transmitted over a distance of more than 1000 km on November 6, 1906). At the beginning of the century, the German physicist Korn created a phototelegraph, which does not fundamentally differ from modern drum scanners. (The figure on the right shows a diagram of Korn's telegraph and a portrait of the inventor, scanned and transmitted over a distance of more than 1000 km on November 6, 1906).
Shelford Bidwell, a British physicist, invented the “scanning phototelegraph”. The system used selenium material and electrical signals to transmit images (diagrams, maps and photographs). Shelford Bidwell, a British physicist, invented the “scanning phototelegraph”. The system used selenium material and electrical signals to transmit images (diagrams, maps and photographs).
Video telephony Personal video telephony on UMTS equipment Personal video telephony on UMTS equipment The latest models of telephones have an attractive design, a wide range of accessories, wide functionality, support Bluetooth technology and wideband-ready audio, as well as XML integration with any corporate applications The latest models of telephones have an attractive design, a wide range of accessories, wide functionality, support Bluetooth and wideband-ready audio technologies, as well as XML integration with any corporate applications
Types of signal transmission lines Two-wire line Two-wire line Electric cable Electric cable Metric waveguide Metric waveguide Dielectric waveguide Dielectric waveguide Radio relay line Radio relay line Beam guide line Beam guide line Fiber optic line Fiber optic line Laser communication Laser communication
Fiber-optic communication lines Fiber-optic communication lines (FOCL) are currently considered the most advanced physical medium for transmitting information. Data transmission in optical fiber is based on the effect of total internal reflection. Thus, the optical signal transmitted by the laser on one side is received on the other, significantly distant side. To date, a huge number of backbone fiber-optic rings, intracity and even intraoffice, have been built and are under construction. And this number will constantly grow. Fiber-optic communication lines (FOCL) are currently considered the most advanced physical medium for transmitting information. Data transmission in optical fiber is based on the effect of total internal reflection. Thus, the optical signal transmitted by the laser on one side is received on the other, significantly distant side. To date, a huge number of backbone fiber-optic rings, intracity and even intraoffice, have been built and are under construction. And this number will constantly grow.
Fiber-optic communication lines (FOCL) have a number of significant advantages over communication lines based on metal cables. These include: high throughput, low attenuation, low weight and dimensions, high noise immunity, reliable safety technology, practically no mutual influences, low cost due to the absence of non-ferrous metals in the structure. Optical electromagnetic waves are used in FOCLs. Recall that the visible optical radiation lies in the wavelength range of nm. Practical application in fiber-optic communication lines received infrared range, i.e. radiation with a wavelength of more than 760 nm. The principle of propagation of optical radiation along an optical fiber (OF) is based on reflection from the boundary of media with different refractive indices (Fig. 5.7). Optical fiber is made of quartz glass in the form of cylinders with aligned axes and different refractive indices. The inner cylinder is called the OM core, and the outer layer is called the OM shell.
Laser communication system Quite an interesting solution for high-quality and fast network communication was developed by the German company Laser2000. The two presented models look like the most common video cameras and are intended for communication between offices, inside offices and along the corridors. Simply put, instead of laying an optical cable, you just need to install inventions from the Laser2000. However, in reality, these are not video cameras, but two transmitters that communicate with each other through laser radiation. Recall that a laser, unlike ordinary light, for example, lamp, is characterized by monochromaticity and coherence, that is, the laser beams always have the same wavelength and are little scattered. A rather curious solution for high-quality and fast network communication was developed by the German company Laser2000. The two presented models look like the most common video cameras and are intended for communication between offices, inside offices and along the corridors. Simply put, instead of laying an optical cable, you just need to install inventions from the Laser2000. However, in reality, these are not video cameras, but two transmitters that communicate with each other using laser radiation. Recall that a laser, unlike ordinary light, for example, lamp, is characterized by monochromaticity and coherence, that is, the laser beams always have the same wavelength and are little scattered.
For the first time, a laser communication between a satellite and an aircraft was carried out, Mon, 00:28, Moscow time The French company Astrium for the first time in the world demonstrated a successful communication by a laser beam between a satellite and an aircraft. The French company Astrium has demonstrated for the first time in the world a successful laser beam link between a satellite and an aircraft. During the tests of the laser communication system, which took place at the beginning of December 2006, communication at a distance of almost 40 thousand km was carried out twice - once the Mystere 20 aircraft was at an altitude of 6 thousand meters, the other time the flight altitude was 10 thousand meters. The aircraft's speed was about 500 km / h, the data transfer rate by the laser beam was 50 Mb / s. The data was transmitted to the geostationary telecommunications satellite Artemis. During the tests of the laser communication system, which took place at the beginning of December 2006, communication at a distance of almost 40 thousand km was carried out twice - once the Mystere 20 aircraft was at an altitude of 6 thousand meters, the other time the flight altitude was 10 thousand meters. The aircraft's speed was about 500 km / h, the data transmission speed by the laser beam was 50 Mb / s. The data was transmitted to the geostationary telecommunications satellite Artemis. In the tests, the aircraft laser system Lola (Liaison Optique Laser Aeroportee) was used, on the Artemis satellite the data was received by the Silex laser system. Both systems are developed by Astrium Corporation. The Lola system, Optics reports, uses a Lumics laser with a wavelength of 0.8 μm and a laser power of 300 mW. Avalanche photodiodes are used as photodetectors. In the tests, the aircraft laser system Lola (Liaison Optique Laser Aeroportee) was used, on the Artemis satellite the data was received by the Silex laser system. Both systems are developed by Astrium Corporation. The Lola system, Optics reports, uses a Lumics laser with a wavelength of 0.8 μm and a laser power of 300 mW. Avalanche photodiodes are used as photodetectors.
Introduction The world is so arranged that any technical invention of the human mind, expanding our capabilities and creating additional comfort for us, inevitably contains negative aspects that can pose a potential danger to the user. Modern means of personal communication are no exception in this regard. Yes, they immeasurably expanded our freedom, "untiing" us from the telephone set on the desktop and giving us the opportunity to contact the necessary correspondent at any time and in any place.
Telephone Cellular mobile phones are actually a complex miniature radio transceiver station. Each cellular telephone is assigned its own electronic serial number (ESN), which is encoded in the microchip of the telephone during its manufacture and communicated by the manufacturers of the equipment to the specialists who carry out its service.
A mobile cellular telephone has a long and sometimes unlimited range, which is provided by the cellular structure of communication zones. The entire territory served by the cellular communication system is divided into separate communication zones or hundredths adjacent to each other. The telephone exchange in each such area is controlled by a base station capable of receiving and transmitting signals on a large number of radio frequencies. A mobile cellular telephone has a long and sometimes unlimited range, which is provided by the cellular structure of communication zones. The entire territory served by the cellular communication system is divided into separate communication zones or hundredths adjacent to each other. The telephone exchange in each such area is controlled by a base station capable of receiving and transmitting signals on a large number of radio frequencies.
Pagers Pagers are mobile radios with letter, digital or mixed message recorder, operating primarily in the 100-400 MHz range. The paging system receives a message from a telephone subscriber, encodes it into the required format and transmits it to the called subscriber's pager.
Fixed wireless radiotelephone Fixed wireless radiotelephone combines a conventional wired telephone, represented by the device itself, connected to the telephone network, and a radio transceiver device in the form of a handset, which provides two-way signal exchange with the base device. Depending on the type of radiotelephone, the range of communication between the handset and the device, taking into account the presence of interference and reflective surfaces, is on average up to 50 meters.
Radio and TV stations Widespread sources of the electromagnetic field (EMF) in populated areas are radio-technical transmitting centers (RTPTS), which emit ultra-short waves of very high (VHF) and ultra-high (UHF) ranges into the environment.
TV station Television transmitters. Television transmitters are usually located in cities. Transmitting antennas are usually placed at an altitude above 110 m. From the point of view of assessing the impact on health, field levels at a distance of several tens of meters to several kilometers are of interest. Typical electric field strengths can reach 15 V / m at a distance of 1 km from a 1 MW transmitter.
Conclusion It is impossible to see electromagnetic radiation, and not everyone can imagine it, and therefore a normal person is almost not afraid of it. Meanwhile, if we sum up the influence of electromagnetic radiation of all devices on the planet, then the level of the natural geomagnetic field of the Earth will be exceeded by a factor of millions. The scale of electromagnetic pollution of the human environment has become so significant that the World Health Organization has included this problem among the most urgent for humanity, and many scientists attribute it to strong environmental factors with catastrophic consequences for all living things.
The work can be used to conduct lessons and reports on the subject "Technology"
This section contains the best reports and presentations on technology and mechanical engineering.
