For the transmission and distribution of electronic data, various means and systems of communication and telecommunications are used.

Let us present the types of communication and the types of information used in them. This:

1) postal (alphanumeric and graphic information),
2) telephone (speech transmission (including alphanumeric data),
3) telegraphic (alphanumeric messages),
4) facsimile (alphanumeric and graphic information),
5) radio and radio relay (voice, alphanumeric and graphic information),
6) satellite communications (also video information).

Communication in an organization is divided into:

Wired and wireless,
- internal (local) and external,
- simplex, duplex and half-duplex.

Duplex mode is when you can talk and hear the other person at the same time. Half-Duplex transmission is a method of bidirectional data transmission (in two directions over one channel), in which information can only be transmitted in one direction at a time.

This is a two-frequency simplex, or half-duplex. From the end user's point of view it is equivalent to simplex.

Simplex mode is when subscribers speak to each other in turns.

Communication line – physical wires or cables connecting communication points (nodes) to each other, and subscribers to nearby nodes.

Communication channels are formed in various ways.

A channel can be created for the duration of a connection between two telephone or radio subscribers and a voice communication session between them. In radio communications, this channel can represent a data transmission medium in which several subscribers can operate simultaneously, and several communication sessions can take place simultaneously.

In this case:

1) wired communications include: telephone, telegraph communications and data transmission systems;
2) wireless communication includes:
a) mobile radio communications (radio stations, cellular and trunk communications, etc.);
b) fixed radio communications (radio relay and space (satellite) communications);
3) optical fixed communication over the air and fiber-optic communication cables.

Communication cables

Twisted pair - insulated conductors, twisted in pairs together to reduce interference between them. There are five categories of twisted pairs: the first and second are used for low-speed data transmission; third, fourth and fifth - at transmission speeds of up to 16, 25 and 155 Mbit/s.

Coaxial cable is a copper conductor inside a cylindrical shielding protective shell made of thin copper conductors, isolated from the conductor by a dielectric. Transfer speed up to 300 Mbit/s. The significant cost and complexity of installation limit its use.

The characteristic impedance of the cable (the ratio between the amplitudes of the incident voltage and current waves) is 50 Ohms.

A fiber optic cable consists of transparent fibers of an optically transparent material (plastic, glass, quartz) with a diameter of several microns, surrounded by a solid filler and placed in a protective sheath. The refractive index of these materials changes along the diameter so that the beam deviated to the edge returns back to the center. Information is transmitted by converting electrical signals into light signals using, for example, an LED. This ensures resistance to electromagnetic interference and a range of up to 40 km.

Telephone communication is the most common type of operational and management communication. It officially appeared on February 14, 1876, when Alexander Bell (USA) patented the invention of the first telephone.

The range of transmitted audio signals via domestic telephone channels is the frequency band 300 Hz–3.4 kHz.

Automatic telephone communication is formed with the help of switching nodes, the role of which is performed by automatic telephone exchanges (ATS), and communication channels (lines) connecting these nodes.

Together with subscriber lines (telephone line from the subscriber to the nearest telephone exchange), it constitutes a telephone network. The telephone network has a hierarchical structure - terminal (intra-institutional, local, district, etc.), city, regional (regional, regional, republican), state and international telephone exchanges. PBXs are connected to each other using trunk lines.

A telephone exchange (PBX) is a building with a set of technical means designed for switching telephone channels.

At the PBX, subscribers' telephone channels are connected for the duration of their conversations, and then, at the end of the negotiations, they are disconnected. Modern vehicles are automatic technical devices (including computer ones).

Institutional PBXs, as a rule, provide not only internal communication between departments with the ability to access external networks, but also various types of production communications (dispatcher, technological, loudspeaker and director) for communication between the director and subordinates, holding meetings and conferences, as well as the functioning of security and fire alarm systems.

The peculiarity of modern automatic telephone exchanges is the possibility of using computer equipment and technology; organizing connections with radiotelephones and pagers. In institutions to overcome high levels electromagnetic fields and partitions, radiotelephones are used that form infrared communication channels.

Local, intra-office or office telephone systems (PBX or PBX) are widely used in organizations. In addition to a wide range of service capabilities, they can significantly reduce the number of city telephone numbers, and also avoid loading city lines and PBXs for conducting local conversations. Mini- and micro-office PBXs are increasingly being used.

There are three main types of wireless networks:

1) radio networks of the free radio frequency range (the signal is transmitted over several frequencies at once);
2) microwave networks (long-distance and satellite communications);
3) Infrared networks (laser, transmitted by coherent beams of light).

Modern wireless networks include:

Radio relay communication;
paging;
cellular and mesh communications;
trunk connection;
satellite communications;
television, etc.

Radio relay communications are formed by building long lines with transmitting and receiving stations and antennas.

It provides narrowband high-frequency data transmission at a distance between the nearest antennas within the line of sight (approximately 50 km). The data transfer speed in such a network reaches 155 Mbit/s.

Trunking (English “trunking”) or trunk (English “trunked”) communication – (trunk, communication channel) - a communication channel organized between two stations or network nodes for transmitting information of a group of users in one radio channel (up to 50 or more subscribers) with a range of 20 to 35, 70 and 100 km.

This is a professional mobile radio (PMR) with automatic distribution of a limited number of free channels among a large number of mobile subscribers, allowing efficient use of frequency channels, significantly increasing system capacity.

Cellular radiotelephone communications (cellular mobile communications, CMS) appeared in the late 1970s. It is also called mobile. SPS systems have been used industrially in the USA since 1983, and in Russia since 1993.

The principle of organizing the SPS is to create a network of equidistant antennas with their own radio equipment, each of which provides a stable radio communication zone around itself (English “cell” - cell).

The SPS uses frequency (FDMA), time (TDMA) and code (CDMA) channel separation methods.

FDMA – frequency division, TDMA – time division multi-access (used in GSM mobile systems), CDMA – code division (signals of other users are perceived by a subscriber of such a network as “white noise”, which does not interfere with the operation of the receiving device).

Another method of wireless communication is optical communication lines (laser or optical communication) using a point-to-point topology.

The method of transmitting sound using a modulated beam of light was proposed at the beginning of the 20th century, and the first commercial devices appeared in the mid-1980s. This communication has high throughput and noise immunity, does not require permission to use the radio frequency range, etc.

Such laser systems support any data transmission protocols. The original signal is modulated by an optical laser emitter and transmitted into the atmosphere in the form of a narrow beam of light by the transmitter and the optical lens system.

On the receiving side, this beam of light excites a photodiode, which regenerates the modulated signal.

Propagating in the atmosphere, a laser beam is exposed to microscopic particles of dust, vapors and liquid droplets (including precipitation), temperature, etc. These effects reduce the communication range, ranging from a few to 10–15 km. The distance also depends on the power of the transmitting devices, which ranges from tens to hundreds of mW and is determined by the need to ensure stable communication. The system ensures communication reliability of more than 99.9%.

Satellite communications

It is formed between special ground satellite communication stations and a satellite with antennas and receiving and transmitting equipment.

It is used for the purpose of providing circular information to a large number of subscribers, as a broadband broadcasting system (television, audio broadcasting, newspaper transmission), for organizing long-distance virtual trunk communication lines, etc. Satellite communications makes it possible to cover territories with poorly developed communication infrastructure, expand the scope and set of services, incl. multimedia, radio navigation, etc.

Satellites are located in one of three orbits.

A satellite using a geostationary Earth Orbit (GEO) is located at an altitude of 36 thousand km from the Earth and is stationary for the observer. It covers large areas (territories) of the planet.

Medium orbits (Mean Earth Orbit, MEO) where satellites are located are characterized by an altitude of 5–15 thousand km, and in low orbits (Low Earth Orbit, LEO) the altitude of satellites does not exceed 1.5 thousand km . In this case, they cover small, local areas.

Satellite communication stations are divided into: stationary, portable (transportable) and portable.

Based on the types of transmitted signals, communication means are divided into analog and digital or discrete.

Analogue signals include continuous signals (electrical oscillations), as a rule, smoothly changing the amplitude of their values ​​during an information transmission session, for example, speech in a telephone channel.

When transmitting any information over data networks, it is converted into digital form. For example, coded sequences of pulses are transmitted via telegraph. The same thing happens when transmitting information between computers via any telecommunications. Such signals are called discrete (digital).

When transmitting information from a computer, an eight-bit binary code is used as a code.

The concept of information is one of the basic concepts not only in computer science, but also in other sciences. Initially, the word “information” meant information transmitted orally, in writing, using conventional signals, and technical means.

Forms of information transfer:

From person to person

From person to computer

From computer to computer

As well as the exchange of signals in the animal and plant world, the transfer of characteristics from cell to cell, from organism to organism.

Information is information, knowledge that is obtained, transmitted, transformed, and registered using certain signs.

Information in technical devices can be transmitted by electrical, magnetic and light impulses.

Information is the product of the interaction of data and methods for their perception. Information exists only at the moment of their interaction; the rest of the time, it is contained in the form of data.

Information carrier - a material object for storing information.

Floppy magnetic disk - designed for transferring small documents from one computer to another. Capacity 1.44MB

Hard magnetic disk (hard drive) - designed for permanent storage of information. Capacity -60-240 GB

Optical (laser) disk - capacity 600MB. The principle of recording and reading is optical.

Hexadecimal number system

The hexadecimal number system, like octal, is an auxiliary system for representing information in computer memory and is used for compact recording binary numbers and teams.

Writing a number in the octal number system is quite compact, but it is even more compact in the hexadecimal system. The first 10 of 16 hexadecimal digits are the usual numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, but the first letters are used as the remaining 6 digits Latin alphabet: A, B, C, D, E, F. The number 1, written in the least significant digit, simply means one. The same number 1 in the next one is 16 (decimal), in the next one it is 256 (decimal), etc. The least significant digit F indicates 15 (decimal). Conversion from hexadecimal to binary and back is done in the same way as for the octal system.

Classification of computer software

information software computer

Software can be divided into two main groups:

1) Application software - performs the user’s task

2) System software (Basic) - controls the entire system, ensures the functioning of the system.

The group of basic programs includes operating systems, while application software is programs designed to work under any operating system.

1)Basic software

Operating system (OS) is a set of programs that provide support for the operation of all programs, PC hardware and networks.

The operating system is controlled by the operating system and all subsequent operation of the personal computer is performed. It is loaded into RAM every time the computer is turned on.

Operating system features:

Organization of dialogue between the user and the computer;

PC resource management;

Launching programs for execution;

Providing a convenient way for the user to work (interface) with PC devices.

MS DOS OS (Microsoft Corporation) has been developed for PCs based on INTEL microprocessors. The MS DOS operating system includes the following main modules:

The basic input and output system is BIOS, which automatically monitors the performance of the main components when the PC is turned on. BIOS programs are located in ROM (read-only memory), and drivers (programs that enable the operation of PC devices) are also located there;

The bootstrap block is designed to be read from system unit into the RAM of other MS DOS modules;

A basic input and output system expansion module that allows you to supplement the BIOS with other drivers designed to work with new devices. Connecting additional drivers for external devices is carried out using CONfIG.SYS files;

The interrupt processing module is a mode of operation of the microprocessor when, at the request of an external device, the execution of the main program is briefly stopped and the external device is serviced, and then the execution of the main program continues;

The command processor is a program that is located in the COMMAND.com file; it receives commands from the keyboard, executes internal MS DOS commands (which are located in the command processor) and launches external commands (which are contained in separate files) for execution.

Disk devices are usually designated by Latin letters: A and B - floppy magnetic disks, C, D and so on are the logical zones of the hard drive and hard drive.

After the OS has successfully loaded, a prompt appears on the screen, which contains the name of the active disk and active title

A file is a named piece of memory on a magnetic medium that contains information. Each file has a designation: name, extension, separated by a dot. Depending on the extension, files have a specific content, so files with the extension txt - text, exe, com - command, executive, BAT - batch, sys - system, files with corresponding extensions can be created in various software (for example, BAS - in BASIC).

A directory is a special place on a disk that contains information about files. It can contain files and other directories, so the disk has a branched file structure (tree).

On IBM PC computers used as user workstations, the following operating systems are most often used:

operating system MS DOS from Microsoft or compatible operating systems PC DOS from IBM and Novell DOS from Novell, etc. We will call these operating systems by the general name DOS;

Microsoft's Windows operating system, more precisely, Windows versions 3.1 or 3.11 or Windows for Workgroups 3.11 (this is an extension of Windows with support for peer-to-peer local networks);

operating systems Windows 95, Windows 98, Windows 2000 and Windows NT Workstation (versions 3.51 and 4.0), Windows Me, Windows XP from Microsoft;

OS/2 3.0 Warp operating system from IBM;

Vista operating systems.

2) Application software is a set of programs executed by a computer system. Application software solves user problems in all areas of his activity. Special software is system and tool programs. System ones perform auxiliary functions: managing PC resources, creating copies of information, checking the functionality of devices, issuing reference information about the computer. Tooling programs provide the process of creating new computer programs.

File managers handle the management file system: creating, renaming, deleting files, and navigating the file system.

Utilities are auxiliary programs that expand and complement the capabilities of the OS. They perform information packaging, verification and treatment computer viruses, sending information over the network, testing and diagnosing a computer, optimizing memory.

While working on a computer, situations arise when information may be damaged or lost, so there is a need to restore it. In this case, copies of this information are needed. They can be obtained using copy commands, but then storing the copy will require the same amount of space as the original. Therefore, it is advisable to use archiving of information, that is, storing it in a compressed form. The archiving process creates an archive file. An archive file may contain one or more files. Archived files acquire the extension of the program used for archiving, for example: ZIP, RAR, IZN, ARJ, ARC. Information in compressed form cannot be directly used. To obtain information in its original form, an unarchiving process is performed - extracting from the archive.

Human activity has always been associated with the transfer of information. The ancient method of transmission is a letter sent by messenger. By talking, we transmit information to each other. Humanity has come up with many devices for quickly transmitting information: telegraph, radio, telephone, TV. Devices that transmit information at high speed include electronic computers, although it would be more correct to say telecommunication networks.

There are two parties involved in the transfer:

source - the one who transmits information,

the receiver is the one who receives it.

Very often, interference occurs during the transmission of information. And then the information from the source to the receiver arrives in a distorted form. Errors that occur during the transmission of information are of 3 types:

some correct information is replaced with incorrect information;

extraneous messages are added to the transmitted information;

Some information is lost during transmission.

Information is transmitted in the form of messages from some source of information to its receiver through a communication channel between them. The source sends a transmitted message, which is encoded into a signal.

This signal is sent over a communication channel. As a result, a received signal appears at the receiver, which is decoded and becomes the received message.

During the transmission process, information may be lost or distorted: sound distortion in the telephone, atmospheric interference on the radio, distortion or darkening of the image on television, errors during transmission in the telegraph. This interference (noise) distorts information. Fortunately, there is a science that develops ways to protect information - cryptology.

Throughout the twentieth century, many ways of exchanging information changed. If in the 19th century the carrier of information was paper, and the means of transmission was the postal service, then in the 20th century information began to be transmitted much faster using the telegraph; information can be exchanged in voice form by telephone; radio and television are intended only for a person to receive information. These days there are a huge number of ways to transmit information, in any form. Telephone lines still remain the most convenient means of transmitting information, but now they serve not only telephones, but also the greatest achievement of the informatization process - the Internet, which contains most of the information from all over the planet.

The computer is the most popular means for processing, storing and transmitting information to this day, but as there is more and more information these days, computers are undergoing significant changes.

For the convenience of users, laptops and pocket computers began to be produced, connected to the global information network Internet, so that the user could obtain the necessary information anywhere, at a time convenient for him.

But since the flow of information is only increasing, it is necessary to develop more and more new means and devices for its creation, processing, storage and transmission. There are many companies and corporations specializing in software development, operating systems, improvement and development of new, more advanced computers, devices for input and output of information, accessories for ease of handling a computer and speeding up information processing.

As for the information itself, a document is still one of the most important ways of transmitting it between people. The information contained in a document can be provided in a variety of forms, most of which are displayed on a variety of media. Text, graphics, video, audio - everything can be transmitted, displayed, distributed and processed as a digital document file.

There are types of very important paper documents that may not have an electronic counterpart.

• 1. This is archival information.
• 2. drawings of manufactured products, developed without the use of automation tools
• 3. documents of your business partners.

Transfer of most of the production process, in which new developments appear, ideas that require development on special programs, which in turn are also being improved and occupy more and more disk space on the computer, poses the task of increasing that same disk space, RAM, new software. This pushes computer corporations to new developments, for example, in the field of exchanging large amounts of data between computers that are not connected to the network.

In all these cases, information is received one-way, that is, the user receives the necessary information by reading it from the media. Is it possible to exchange electronic information ( text documents, drawings, drawings, audio and video documents) bilaterally? Of course, you can if your computer is connected to the Internet and has the necessary hardware and software.

Internet video conferencing is a very cost-effective alternative to traditional proprietary systems, but they require communication channels with higher bandwidth than Internet telephone conversations, so they attract the attention primarily of users from the business world.

Internet collaboration products feature a variety of interactive technologies that enable close collaboration and information sharing among members of impromptu workgroups. Several users can work together with one application program, discuss emerging ideas, discuss and exchange files

But, regardless of whether it is a large corporation or a small company, a new problem has arisen - the problem of network security.

In recent years, thousands of companies have installed Web sites and their employees have access to e-mail and Internet browsing programs. As a result, any outsider with basic knowledge of network technology and bad intentions now has a way to penetrate a company's internal systems and network devices: through the Internet communication channel. Once inside, the “burglar” will find a way to obtain the information he is interested in; destroy, alter or steal data. Even the most widely used Internet service, email, is inherently vulnerable: anyone with a protocol analyzer, access to routers, and other network devices involved in processing email as it travels from one network to another via the Internet, it can read, change and erase the information in your message unless special security measures are taken.

Manufacturers of networked information security products have quickly responded to the needs of the Internet, adapting existing authentication and encryption technologies for Internet communication channels and developing new security products.

COMMUNICATION AND COMMUNICATION MEANS

Classification of office equipment

Office equipment – These are technical means used for mechanization and automation of management and engineering work. In a broad sense, office equipment can include any device (device, device, tool) that is used in the office of a company, from pens and pencils to computers and complex electronic office equipment.

The functioning of a modern tourism enterprise is directly based on the use of information processing technologies and office equipment.

According to their purpose, they can be divided into the following groups:

• means of communication and communications;
• office equipment;
• copying equipment;
• means of collecting, storing and processing documents, which primarily include computers and computer networks;
• scanners;
• means of displaying information;
• devices for destroying documents.

Methods of transmitting information

On modern stage The development of means of communication and communications play an important role in ensuring effective management of the tourism business. Any delay in information may result in very serious negative consequences both financially and in the loss of the company's image, which can ultimately lead to the collapse of any organization. This directly applies to enterprises in the tourism and hospitality industry.

Information transfer can be carried out manually or mechanically using automated systems through various communication channels.

The first way to transmit information and is still widespread today. In this case, the information is transmitted either by courier or by mail. The advantages of this method include complete reliability and confidentiality of the transmitted information, control over its receipt (when sent by mail at registration points), minimal costs that do not require any capital expenditures. The main disadvantages of this approach are the low speed of information transfer and slowness in receiving answers.

Second way significantly increases the speed of information transfer, increases the efficiency of decision-making, but at the same time capital and current costs increase. With proper organization of the production process at an enterprise, this method of transmitting information ultimately significantly increases economic efficiency functioning of an enterprise in the tourism and hospitality industry.

To transmit information, you need: a source of information, a consumer of information, transceiver devices, between which communication channels can exist. In general, this process can be represented as a sequence of the following blocks (see figure)

With manual or mechanical transmission of information, people are involved at each stage; with automated transmission, various electronic instruments and devices can be used. One of the problems that arises during the automated transmission of information is the quality of information transmission, which is significantly reduced due to interference occurring in communication channels and in transceiver devices. To reduce the latter, improve the quality of transmitted information and ensure its reliability, special circuits are built into transceiver devices. The less interference, the better the automated systems work.

The quality of the system as a whole must be assessed by indicators such as throughput, reliability and reliability of the information received.

Under throughput system implies the maximum amount of information that can theoretically be transmitted per unit of time. Bandwidth is determined by the speed of information conversion in transceiver devices and the possible speed of information transfer in communication channels, depending on physical properties both the channel and the signal itself.

Under reliability refers to the transmission of information without distortion.

Under system reliability refers to the ability to perform specified functions while maintaining its basic characteristics within established limits. Reliability is associated with such concepts as “failure-free operation”, “durability”, “maintainability” and “storability”. Reliability indicators of any system are the probability of failure-free operation, time between failures, technical resource, service life, etc.

Data transfer protocol is a set of rules that determine the data format and procedures for transmitting it over a communication channel.

The history of mankind knows examples of amazing ways of transmitting information, such as knotted writing, Indian tribes called wampum and encrypted manuscripts, one of which cryptologists still cannot solve.

Knotted writing in China. Photo: Commons.wikimedia.org

Knot writing, or a method of writing by tying knots on a string, presumably existed before the advent of Chinese characters. Knotted writing is mentioned in the treatise Tao Te Ching (“Book of Path and Virtue”), written by the ancient Chinese philosopher Lao Tzu in the 6th-5th centuries. BC Interconnected cords act as information carriers, and the information itself is carried by the knots and colors of the laces.

Researchers put forward different versions of the purpose of this type of “writing”: some believe that the knots were supposed to preserve important historical events for their ancestors, others believe that ancient people kept accounting in this way, namely: who went to war, how many people returned, who was born and who died, what is the organization of the authorities. By the way, knots were woven not only by the ancient Chinese, but also by representatives of the Inca civilization. They had their own knotted writing “kipu”, the structure of which was similar to the Chinese knotted writing.

Wampum. Photo: Commons.wikimedia.org

This writing of the North American Indians is more reminiscent of a multi-colored ornament than a source of information. The wampum was a wide belt made of shell beads strung on cords.

To convey an important message, the Indians of one tribe sent a wampum-carrying messenger to another tribe. With the help of such “belts”, treaties were concluded between whites and Indians, and the most important events of the tribe, its traditions and history were recorded. In addition to the informative load, wampums carried the burden of a currency unit, sometimes they were simply used as decoration for clothing. People who "read" wampum had a privileged position in the tribe. With the advent of white traders on the American continent, shells were no longer used in wampum, replacing them with glass beads.

Rubbed iron plates

The glare from the plates warned the tribe or settlement of the danger of attack. However, such methods of transmitting information were used only in clear sunny weather.

Stonehenge and other megaliths

Megalithic burial in Brittany. Photo: Commons.wikimedia.org

Ancient travelers knew a special symbolic system of stone structures or megaliths, which showed directions of movement towards the nearest settlement. These stone groups were intended primarily for sacrifices or as a symbol of the deity, but they were also practically road signs for the lost. It is believed that one of the most famous monuments of the Neolithic era is the British Stonehenge. According to the most common version, it was built as a large ancient observatory, since the position of the stones can be associated with the location of celestial sanctuaries in the sky. There is also a version, which does not contradict this theory, that the geometry of the location of stones on the ground carried information about the lunar cycles of the Earth. Thus, it is assumed that ancient astronomers left behind data that helped their descendants deal with astronomical phenomena.

Encryption (Voynich Manuscript)

Voynich manuscript. Photo: Commons.wikimedia.org

Data encryption has been used since ancient times until now, only the methods and methods of encryption and decryption are being improved.

Encryption made it possible to transmit a message to the person to whom it was intended in such a way that no one else would be able to understand it without the key. The forefather of encryption is cryptography - mono-alphabetic writing, which could only be read with the help of a “key”. One example of a cryptographic script is the ancient Greek scytale, a cylindrical device with a parchment surface whose rings moved in a spiral. The message could only be deciphered using a stick of the same size.

One of the most mysterious manuscripts recorded using encryption is the Voynich manuscript. The manuscript received its name in honor of one of the owners, the antiquarian Wilfried Voynich, who acquired it in 1912 from the Roman College, where it had previously been kept. Presumably, the document was written at the beginning of the 15th century and describes plants and people, but it has still not been possible to decipher it. This made the manuscript famous not only among cryptographers, but also gave rise to all sorts of hoaxes and speculation among ordinary people. The bizarre texts of the manuscript are considered by some to be a skillful forgery, by others as an important message, by others as a document in an artificially invented language.