A modem is a device that receives and transmits a signal. Characteristic feature: speech usually concerns exclusively computer technology, analog tandems are called transceivers. Digital systems primarily use two bands: radio and optical. Communication is wired or wireless. In accordance with this gradation, the discussed transceiver devices were created. The etymology of the term is formed by the names of two processes that are opposite in meaning: modulation, demodulation. Computers today use exclusively digital signals.

The modulation process ensures the survival of information in the environment. Fast decay first low frequencies Popov noted. The Russian researcher figured out how to change the parameters of electromagnetic vibrations according to the law of transmitted information. The process is called modulation. Popov used amplitude, half a century later frequency appeared, today the words running to the computer are predominantly pulse-code modulation, introduced into use by the Americans who carried out military actions against the Axis countries. The description of the Green Hornet system is publicly available.

Operating principle

Any medium is formed by particles and molecules. Mechanical waves cause periodic cyclic shifts of substances. The nature of electromagnetic oscillations and the mechanism of their occurrence have not yet been explained. However, the properties and distribution characteristics have been well studied. The media are (mainly):

1. Atmosphere of the Earth.
2. Copper.
3. Optical glass.

Numerous types of modems have been created that convert protocols: Wi-Fi, 4G, Ethernet. The start and end signal is always a sequence of digital information pulses. They are manipulated by the processor, front bus, RAM. However, the digital signal spectrum does not penetrate the medium well: copper wire, ether. Electromagnetic vibrations are completely powerless to pass through PON fiber; light or similar ranges (infrared, ultraviolet) are already required.

Environment characteristics

• Own capacity.
• Inductance.

The above determines the presence of resonant characteristics of the system. Simply put, there is a certain frequency that passes perfectly through a twisted pair cable, coaxial cable, or communication cable. If you centralize the signal spectrum around this peak, the network range greatly increases. A similar picture is demonstrated by optical fiber, also endowed with frequency characteristics. The above explains the need to design converters sold by manufacturers via modems.

Terms

Modulation is the process of changing the parameters of a carrier frequency according to an information message.

Demodulation is the extraction of a signal embedded by the transmitting side for subsequent use.

The modulated signal propagates perfectly along the cable, optical fiber (light), and ether. The receiving side modem performs demodulation.

A radio signal is a carrier frequency modulated by information.

The video signal is a typical rectangular pulse.

Environments used

Constant competition forces manufacturers to move. Organizations issuing certificates are constantly receiving new samples. Latest version Wi-Fi... has overtaken gigabit Ethernet in bitrate. The IEEE 802.3an-2006 release provides ten times the speed over a distance of 100 meters. Long range options available.

In the same year that IEEE 802.3an was released, a group was created that planned to conquer the 100 Gbit/s barrier. The first versions of Ethernet (10 Mbit/s) used coaxial cable, subsequent ones began to use twisted pair and optical fiber. Increasing the frequency greatly increases throughput channel. This property has become the main reason for using LEDs.

Similarly, the frequency of ethereal waves increases. Initially, Wi-Fi used the 900 MHz region, then the standards became:

1. 2.4 GHz.
2. 5 GHz.

Today there is a tendency to develop the 60 GHz region. Router antennas operate in parallel, information is transmitted in four or eight streams.

Key difference between modems

The attentive reader will notice that computer communications often carry a bare digital signal, devoid of a carrier (for example, a monitor channel). Russian-language sources give an example of the difference between a router and a modem:

The router is often devoid of modulating and demodulating devices and deals exclusively with redirecting the data flow.

Reminds me of nonsense? However, the answer is partially correct.

Difficulties in classification

Eliminating the need to use a carrier significantly speeds up the process of information transfer. The router's associative RAM increases performance. However, the English Wikipedia domain (en.wikipedia.org/wiki/Modem) describes the situation regarding early Ethernet (10 Mbit/s) implementations as follows:

“Often, even when installing a cable, there is a need to use radio signals (modulation). Coax provides incredible bandwidth, but digital video attenuation is becoming a huge problem. Using a modem, we get a much higher bitrate. Cable television and the Internet more often operate with radio signals, ensuring that the needs of a growing customer base are met. At the same time, frequency division of channels becomes possible - full duplex is provided by a single line.”

The second aspect is Ethernet's collision avoidance technique. A country about to transmit a message first checks that there is no carrier. Think about it, this is an RJ45 interface: network card, router, line connecting the ADSL modem to the PC. It is the “1-persistent CSMA” system that the Ethernet protocol uses.

You know, any reviews that touch on the topic are missing an important detail. Where exactly do devices catch the carrier, what kind of carrier? Mobile networks the first generation, for example, used separate frequency, placed outside the main channel band. Based on this state of affairs, many began to equate the modem and the Ethernet network card.

Answer

The answer is hidden by the name itself Ethernet technologies. It includes the word BASE, meaning: Baseband signaling.

The bits undergo 4B5B encryption, pulse shaping, and then NRZI encoding. The resulting signal is simply transmitted to the cable. For 100BASE-T the average frequency is 31.5 MHz. For some unknown reason, the literature calls the resulting spectrum a carrier spectrum, although the cable transmits a typical video signal. This is what the equipment tries to catch before transmitting. There is no carrier here!

How to classify

The modem always performs signal conversion. For a copper core, the process is not obvious - there is no fact of a change in the environment. Therefore, a typical RJ45 (8p8c) port cannot be called a modem. Inside the PC there are brass busbars, outside - twisted pair. Connecting optical fiber and using airwaves, on the contrary, always has something to do with the modem.

1. An LED is needed to convert electrical vibrations into light.
2. Antennas USB Wi-Fi adapter are engaged in the emission of ethereal waves.

The receiving side performs similar transformations. It is the issue of speed that is the primary reason for the use of PON by providers everywhere when covering the last mile of Internet access mainly with twisted pair cables. According to publicly available sources:

A modem is commonly called a wired communication modulator-demodulator.

Wireless ones are more likely to be transceivers, transceivers. Simply put, there is no elementary theoretical basis supporting the development of domestic network technologies.

Attention, question

How then should we interpret fiber optic Ethernet technologies? The name BASE is retained by inertia. This assumes that there are no additional spectrum conversions relative to the twisted-pair variants, in addition to those performed by the LED. The submillimeter frequency automatically acts as a carrier. Therefore, any router containing a fiber optic port can (and should) be called a modem. Although formally the signaling remains a video signal (Baseband).

The final demarcation

Taking into account the above, we will definitely call the devices a modem:

• Wireless communication. Because a radio wave is emitted.
• Fiber optic. Signal conversion occurs at the interface of two dissimilar conductor-glass media.
• Performing modulation/demodulation within copper networks: ADSL, Dial-up and others. Ethernet (RJ45) does not apply here for the most part.

History of dial-up: telephone lines

Wikipedia is inclined to consider the first multiplexers to be modems. For example, devices that used (second half of the 19th century) the transatlantic cable. However, we consider such a free interpretation unnecessary. The first systems were controlled exclusively by current, the signals being Morse code symbols. The further narration of the world encyclopedia is quite acceptable. The starting point is considered to be 1941, the time of the creation of the SIGSALY system, codenamed Green Hornet.

The speech was digitized by a vocoder, so the transceiver device could well be called a modem. It was the Allied troops who were the first to use phase manipulation. Further developments are, to put it mildly, classified. It is only known that long before the appearance of the first (known to the scientific community) computer networks Modems were already connecting parts of the SAGE air defense computing complex, designed to control NORAD's response to a hypothetical Soviet attack.

Therefore, the year of birth of modems is called 1958. The term has been used since 1937, characterizing analog transformations of mechanical and electrical waves. However, today the concept has been completely occupied by computer scientists. SAGE modems connected command centers, terminals, bases, radar stations. Products are described by a specialized AT&T standard.

First bird

The Bell 101 dataset was the first commercial success. A year later (after shipment to the military), the models were made public. The stated transmission speed is 110 baud. Digital data was transmitted by any telephone line. The devices were the first to use the ASCII alphabet. Therefore, they quickly received the name “four rows”; the actual octet, composed of two hexadecimal digits, is still used today. Previously, they used the “3-row” Baudot code (6-bit), which was dominant in the period 1908..1962.

Second generation (1962) – Bell 103 acoustic modems reached 300 baud. The equipment used frequency manipulation of sound vibrations. Duplex channel applied:

1. Request 1270 Hz (one)/1070 Hz (zero).
2. The answer is 2225 Hz (one)/2025 Hz (zero).

Although the old stuff has long been thrown out, Bell 103 compatibility certificates continue to be used today. For a long time remained backward compatibility new iron. The modulation method is popular among amateur radio, HF radio, and commercial applications. The amazing reliability of the technique maintains reliable reception in incredibly harsh conditions.

Development of communication technology

Even then, a four-wire duplex system was used, providing speeds of 2000 (210A) - 2400 (201V) bps. 1968 brought a revolutionary idea put forward by the FCC: a line could be loaded with electrical devices at the same time. Acoustic modems need a narrow band of 1-2 kHz. The vast majority of devices based on General Electric patents were fully capable of working together. Well-known models of acoustic modems from the 70s:

• CXR Anderson-Jacobson
• Novation CAT
• Pennywhistle modem
• AT&T 212A
• Vadic VA3400, VA3467

The devices helped the first commercial models of personal computers (Apple II) communicate. Only the new Hayes Smartmodem 300 (announced on April 27, 1981), which helped the developers of the first electronic bulletin boards, finally destroyed the SEALs' monopoly.

CAT used Bell 103 (300 bps), 202 (1200 bps) encoding systems. The first option is very bulky and took up the expansion slot of an Apple PC. Thanks to its internal installation (as opposed to the RS-232 port), the device supported a wide range of commands and generated error reports. It was the introduction of internal slots (Apple S-100) that helped create truly software-driven models.

80s

The real boom of the early 80s was caused by rapidly falling prices for electronic components. The release of the Hayes line provoked a rapid growth in the number of electronic bulletin boards, creating the preconditions for the emergence of Fidonet. The company provided the developers with a number of built-in instructions for performing a variety of actions. Smartmodem was the first external device to support control via the RS-232 interface.

Increasing speeds allowed enthusiasts to transfer files by adding BBS services electronic libraries. Tom Dennings, creator of Fidonet, sent updates remotely software subscribers in full automatic mode. Instead of two (see above), they began to transmit more frequency symbols - 4, 8. Each contained 2, 3 bits at once, significantly increasing the data transfer speed. 2400 bps has become the de facto standard.

Three American whales

Three companies offered the first subscribers to connect devices to the network (the Internet did not exist then) of telephone companies:

The success of new products was brought by the ability to correctly set the speed. Automatic detection bitrate ensured compatibility with outdated types of devices, maintaining the “legacy of the difficult past.” The algorithm is outrageously simple:

1. The newcomer started calling.
2. Not receiving a response, I lowered the bitrate to get a response.

There were overlaps. The V.32 and HST models turned out to be incompatible. Both supported a speed of 9600 bps, but the difference in implementations forced them to use 2400. A similar problem befell the creations of the USRobotics company.

Computer racing

The 90s brought rapid increases in speed, making equipment cheaper. In 1998, the 56 kbit/s milestone was overcome by using information compression technology together with pulse code modulation. The speed of progress has set new limits:

1. Archived files – 50 kbps.
2. Text – 320 kbit/s.
3. Other – 160 kbit/s.

It was necessary to introduce a local memory buffer because the compression algorithms were uneven. At the same time, the first Internet sites began to actively use compression technologies and use of subscriber power (for example, Flash applications).

Evolution of options

Modern speed appeared gradually.

Echo suppression

Experts called echo suppression a revolutionary step. Local telephone networks low quality caused the signal to be reflected. Sometimes people like to hear faint echoes of their own voice, since the fact that there is a response indicates that the line is working. However, modems are powerless to distinguish their own echo from a request from a modem located on the other side of the line. The first devices used the extension of the request signal beyond the response signal. The bitrate suffered.

The new echo cancellation system sent a unique sound tone outward and began listening for feedback. Then I set the delay time for the inverted response. The phases of the two added signals were set to be opposite. The echo was completely extinguished. Modems received the full spectrum at their disposal.

Quadrature modulation

Quadrature modulation helped double the bitrate (compared to frequency shift keying). Two carrier frequencies (1650 kHz) are transmitted together with a phase shift of 90 degrees. The final value was 9600 bps instead of 2400 baud. Contemporaries decided that the theoretical limit of information compression had been reached. In 1968, a new product cost $20,000.

Trellis modulation

The year 1982 brought the world a document that became a new frontier in the development of the direction. Gottfried Ungerbock proposed encoding parity bits arranged in a 2-dimensional diamond pattern. With the same number of failures, the bitrate doubled. The technique is called Trellis modulation.

Trellis matrices were introduced by Dave Forney (1973). Almost all products that reached 9600 bps used a convolution code and the Viterbi algorithm.

Error correction codes

The introduction of redundancy helped to correct errors or recognize “broken” words.

ADSL

Acoustic modem technology has quickly reached its stride. Increasing the bitrate required mastering the ultrasound spectrum (extends to units of MHz). The capacity of telephone (American standard) twisted pair cable exceeds the needs of telecom operators with a margin (maximum limit 3.5..5 kHz). There remains a gigantic space. It is this fact that asymmetric digital communication technology takes advantage of.

ADSL covered the last mile section most successfully. Asymmetric transmission is called due to the characteristic spectrum distribution:

1. Upload – 26..137 kHz.

The space is divided by relatively narrow (4.3125 kHz) container channels. The modem examines the available bins one by one, assessing the signal-to-noise ratio in order to optimize speed characteristics. Already the first versions (1984) exceeded the cherished threshold of 100 kbit/s. ITU-T G.9700 (December 2014) provides download speeds of 100 Mbps. Canadian DSL Rings technology uses existing copper telephone networks to achieve speeds of 400 Mbps.

• The fundamental difference between ADSL technology and dial-up is the use of significantly higher spectrum areas. The result was an expansion of the channel's capacity.

The theoretical foundations were summed up (1948) by Claude Shannon, who wrote the work Mathematical Theory of Communication:

• Increasing the bitrate requires expanding the bandwidth. The relationship is nonlinear, since new digital processing techniques are constantly emerging*.

* Apparently, the researcher meant the creation by the Americans of the Green Hornet digital communication system (1941).

DSL modem

Peculiarities:

1. Connection to a telephone line for digital services.
2. Docking with a PC via USB, Ethernet, PCI.

They even produce DSL routers, including those containing an access point. Characteristic appearance of an external modem:

1. RJ11 connector for telephone line input.
2. RJ45 or USB for connecting to a PC.
3. A set of LED indications showing channel activity.
4. Configuration via browser or included software.

Story

Beginning in the 50s, the military used telephone lines. However, twisted pair cables were also used by film studios. It turned out that the line completely passes 4 television channels in the HF region. For example, the British route BBC-Pontop Pike is 16 km long. In this case, the picture was quite crappy, giving only a general idea of ​​​​what was happening.

However, the beginning of the 80s brought the world cable broadcasting, significantly expanding its former boundaries. US Patent 4,330,687, filed March 14, 1979, proposed sharing computer and telephone on one twisted pair cable. A logical continuation (1984) was the creation of ISDN digital cable broadcasting regulations. Bellcore staff placed transmission above the voice video signal by modulating the carrier. A 1998 standard (US Patent 4.924.492) established the technology.

Formulation of the asymmetric channel concept

Joseph Lechleider showed the double advantage of an asymmetrical line over a symmetrical one. Internet providers quickly appreciated the new product. ADSL began to support two modes:

1. Fast.
2. Alternating channels.

The first one perfectly transmitted a stream of multimedia data (video, sound), allowing for the presence of faulty bits of information. Interleaved mode transferred files better, but was slower. Providers had to learn existing networks with network switching (not packet). HDSL and SDSL technologies fully ensured the delivery of Digital Signal 1, using Bell labs developments, to the consumer.

Interface improvements

The oldest varieties provided a speed of 8 Mbit/s on an unshielded twisted pair line at a distance of 2 km. Further increase in range required the use of repeaters. The growth of popularity was restrained by the relatively high price. The situation was corrected by the VLSI output (super-large integrated circuits). ADSL reigned supreme for about a decade, starting in the late 90s.

First varieties digital channels timidly used the 10..100 kHz band. Gradually the upper limit reached 1.1 MHz. Later the strip began to be divided in two:

1. Data upload area.
2. Loading area.

The line was closed by modems engaged in carrier modulation. The decrypted data was transmitted to computers, routers, and hubs. A small drawback is that the signal is unable to pass through the Pupin coil. Old telephone lines periodically contain similar devices that increase communication range. Gradually, service providers replaced the old cable system by laying optical fiber.

Routers became connecting devices (Ethernet, Wi-Fi, Powerline). It looks strange, but naked DSL networks are still popular worldwide. In 2012, in the USA it was reported that obsolete ADSL lines were being replaced with optical ones.

Other technologies

According to the above classification, there is a lot of equipment servicing optical lines. The operating principle of absolutely all converters can be adjusted to the modem. Deserves a separate discussion wireless technologies, including Wi-Fi, Bluetooth, equipment mobile operators, infrared ports, satellite communications. Such an extensive list of devices has led to the emergence of new terms.

The transceivers that decorate parabolic antennas (dishes) are usually called transceivers. Bluetooth and Wi-Fi equipment have unfairly occupied the niche of adapters. Although this class of equipment deals specifically with modulation. An ordinary adapter simply converts the type of signal. Example: typical charger:

• Input: 220 V 50 Hz.
• Output: constant voltage 4-12 V.

Finally, the well-known walkie-talkies (walkie-talkies) also do modulation/demodulation. Previously, skeptics could argue that the signal was analog, but today any Motorola operates with digital codes.

Summarizing what has been said, we can unequivocally state: the terminology of the field of digital communications remains incomplete. Adding to the problem is the inaccuracy of the Western classification of devices. The result is unclear knowledge of domestic specialists regarding the real state of affairs. As they say, rely on Windows, but don't make a mistake yourself.

What is a modem and why is it needed?

Its name comes from two words: MODulator and DEmodulator. These two words perfectly reflect the essence of the work performed by the modem. It modulates the signal transmitted to the telephone line with information received from the computer, and vice versa, transmits to the computer what it demodulated from the line. Why is this necessary? - a meticulous reader will immediately ask. But why! As you probably know (and if you don’t know, read more carefully!), all information is represented on the computer in the form of zeros and ones. Zeros and ones, in turn, are encoded by voltage: no voltage - zero, voltage - one. Naturally, computers can only exchange information using zeros and ones. If the distance over which data needs to be transferred is small, such as in a computer - from one microcircuit to another, they are simply connected by wires. What if you want to transfer something to the computer of a friend who is, say, in another area? You will go broke just buying the wire, not to mention having to dig a ditch for this wire, or hang it on poles (otherwise they will get lost!).

Fortunately, the telephone has become widespread in many places - and this is nothing more than a ready-made pair of wires. However, these wires are not as good as we would like, because they are still intended to transmit voice, and not zeros and ones. This is where the modem comes in: converting the zeros and ones into a signal that is more or less similar in its characteristics to a voice, and therefore suitable for transmission over the telephone. At the same time, the modem also performs functions typical for regular phone, - dials a number, picks up when they call, etc.

In order to perform all the functions assigned to it, the modem must be very smart, and this is not easy even for people. Essentially the modem is small computer. It has a processor, memory, and all sorts of other parts necessary for normal operation. It connects to the telephone line at one end and to the computer at the other. If we have sorted out the telephone line a little, then it’s worth saying a few words about connecting to a computer. Computers - they are also different, big and small, fast and not so fast. In order not to make a different modem for each type of computer, smart people decided to come to an agreement and install the same device in all computers - a communication port (COM port).

If the computer has such a communication port (the standard for it is called RS232C in America, and V24 in Europe), then any standard modem can be connected to it. Naturally, we need to immediately clarify what we mean when we talk about a “standard” modem. Modems, as such, are covered by three types of standards: you already know about one of them - it describes the interaction of the modem with a computer (RS232C/V24), the other determines how data is converted for direct transmission over the phone, and the third describes commands to the modem (by the modem too you can command!).

Let's take a closer look at the standards for data transmission protocols over the telephone network. The speed at which it operates, as well as the very possibility of its operation with any other modem, depends on what protocols your modem supports. Generally speaking, the principle of transmitting information over the telephone is somewhat reminiscent of radio. The modem generates a so-called carrier frequency (“our radio station operates on the frequency...”), and modulates it with information received from the computer according to the rules of a specific protocol. (Very often you will come across the English word CARRIER - don’t be alarmed, it means the carrier frequency). The most common protocols are V21, V22 and V22bis. They determine how signals must be modulated to transmit information over telephone lines at speeds of up to 300, 1200 and 2400 bits per second, respectively. It should be noted here that data over the phone is transmitted sequentially, bit by bit, and in addition to the basic information for which everything is started, service information necessary to “keep the conversation going” is also transmitted. Typically, in addition to the 8 bits of each data byte, 2 bits are added: one at the beginning (start bit) and one at the end (stop bit). Total: a byte will consist of 10 bits, therefore in our case the maximum transfer rates are useful information will be 30, 120 and 240 bytes per second.

Science naturally does not stand still, and recently new protocols have appeared that increase speed and provide additional services. Examples include the MNP and V42/V42bis protocols. Modems that support them can automatically correct errors that occur during transmission and compress the transmitted information, which sometimes increases performance. The V32 and V32bis transmission protocols describe a method for transmitting data at speeds of up to 14,400 bits per second, with the ability to automatically reduce or increase it during transmission depending on the quality of the line. As a rule, modems maintain upward compatibility. That is, modems that support more advanced exchange protocols nevertheless do not stop working with older models. The most important thing is that these old models are standard, which cannot be said about some crafts made by domestic craftsmen. Despite the attractive advertising (“1200!”, “2400!”, “high reliability!”), they are only able to connect to themselves, not to mention the fact that some of them, along with the signal, push a lot of interference into the line than is natural cause the ire of signalmen.

Now let's look at the third type of standards - this is the standard for modem commands. In order to clarify what a “modem command” is, I will make one clarification: for any standard modem, there are two possible modes in which it can be. The first mode is data transfer mode. The modem receives data from the computer, converts it into a signal, and sends it to the telephone line. Similarly, the signal that came from the line is converted into data and transmitted to the computer. The second mode is team mode. In this mode, the modem does not perform any modulation/demodulation and does not send anything to the line. It considers all the data that comes to it from the computer as commands and tries to execute them. This mode is the basic mode for the modem, that is, when you turn on the modem, it starts working in command mode. In this mode, you can send various commands to the modem, force it to pick up or put down the handset, dial a number, turn on or off the speaker, and configure data transfer parameters.

The standard for commands proposed by the American company HAYES (read [hayes]) is currently generally accepted. This is usually written as "HAYES compatible command set", but sometimes it is also called "AT" compatible set - after the first two letters that indicate the command. It is by these first letters that the modem understands that the entered information must be understood as a command to be executed. In your experiments, you should keep in mind that any command to the modem should be no longer than 40 characters, and end with a “carriage return” code (ENTER key), although there are a few exceptions, which we will look at later. If the modem recognizes the command, it tries to execute it and report the result. The simplest command consists of just two letters “AT”; it forces the modem to “give voice” and answer that everything is fine with it. This response looks like an "OK" message from the modem. As a rule, modems are automatically configured for the speed and other parameters of the COM port to which they are connected, so that any working standard modem that is in command mode should respond to this simple command. If the modem cannot understand the nonsense that has fallen on it, it swears “ERROR”, which means an error.

Nowadays, the Internet is needed almost always and everywhere. Moreover, this applies not only to city everyday life, when we can get 3G or 4G from a smartphone or tablet almost anywhere in the city. If we talk about a laptop, then we can, of course, find a Wi-Fi network or distribute the Internet from a smartphone. But you must admit, this is not possible and not so convenient everywhere. And what can we say about country trips, when getting 2G is already quite good, and free networks We can only dream of Wi-Fi. Okay, a smartphone or tablet, but what about a laptop? What if there is a desktop computer at the dacha? What if they call you from work? It would be possible to complete urgent tasks right outside the city, but there is no Internet, so you have to go home.

On long trips you also need the Internet: on business trips - for work, on tourist trips - to study maps, search interesting places, publishing photos on Instagram and others social media. Do you really have to search for Wi-Fi forever or distribute the Internet from your phone?

Modems and mobile routers will come to the rescue. The principle of their operation is simple: insert a SIM card and enjoy the Internet. The signal strength depends only on the coverage area of ​​your operator. “Great!” - you say and open the page with modems. And there are so many of them... And such different prices... How to choose? It all depends on how exactly you want to use the gadget. It is important what devices you will connect to it, as well as where you will use it.

An important point is the choice of operator. The signal level, and, consequently, the data transfer speed depends on it. Many operators offer their own “branded” modems. They have two disadvantages. The first is that they are often more expensive. Secondly, you will only be able to use the services of this operator. If in the place where you are, its networks do not work - well, alas. Therefore, we suggest considering modems and mobile routers from third-party companies.

How are modems different?

USB modem or mobile router

A USB modem is a transceiver that uses operator networks mobile communications for transmitting and receiving information. It connects to the USB connector of your computer and after a little setup allows you to use the Internet. It can also be used with a regular router. A SIM card is inserted into the USB modem, the choice of which depends only on the coverage of the operator’s network in the location you need. All USB modems are very small and lightweight, allowing you to carry them in a bag or pocket.

A mobile router is a device that operates on the principle of an ordinary modem. A SIM card is inserted into it, the device receives a signal mobile operator and, unlike a USB modem, provides mobile Wi-Fi. Such a gadget is usually powered by a battery, which requires regular charging. Mobile routers are not as small as USB modems. Some models can be put in your pocket, while others will only fit in a bag.

To choose between these two types of gadgets, answer the question: what do you need this device for? If you want to use it only with a laptop to have Internet anywhere, or with a desktop computer, purchase a USB modem. If you are interested in a portable Wi-FI access point for connecting a number of devices, it is better to purchase a mobile router.

3G or 4G

3G and 4G are technologies wireless communication, which allow you to get high-speed Internet access from mobile devices. The letter G in their names comes from the word “generation”, that is, “generation”. Therefore, 3G is the third generation of wireless communications, and 4G is the fourth.

The main difference between these two generations is the data transfer speed. 3G networks are capable of transmitting data at different speeds, which depend on the operating frequency of the mobile operator. Leading operators have an operating frequency of 15 MHz, while some small ones have only 4.5 MHz. Therefore, the speed range of 3G networks ranges from several hundred kilobits to several tens of megabits per second.

The main advantage of 3G networks is their coverage area, which covers most of the territory of Russia. Also a plus will be the low cost of modems that only work with 3G.

4G networks are capable of transmitting data at much higher speeds – up to 1 Gbit/s. True, this depends on the type of device: for example, not all mobile devices will be able to achieve a speed of 100 Mbit/s.

The downside of 4G networks is the poor coverage in Russia: it only covers large cities. Also, due to high-speed data transfer, devices working with 4G have higher power consumption.

So, when choosing a gadget for your dacha or travel, it’s better to go with a 3G modem, since you’re unlikely to get 4G anyway, and you’ll spend less money on the device. For the city, a 4G modem is better suited.

GSM, GPRS, EDGE, HSPA, LTE

All these scary abbreviations are nothing more than communication standards and technologies of different generations.

GSM is the main second generation communication standard. A packet transmission technology has been created for it. GPRS data, the transmission speed of which can reach 115 kbit/s.

EDGE is a packet data transmission technology used by the second generation CDMA communication standard. The speed with it reaches 384 kb/s. By the way, this is the same E,
which is displayed on the screen of a smartphone or tablet when it does not receive 4G, 3G, or H.

HSPA is a third generation communication standard that allows you to achieve a packet data transfer speed of 42.2 Mb/s. And this is the same H.

LTE is the fourth generation data transmission technology, the speed of which reaches 1 Gb/s.

All these standards and technologies are actively used by Russian telecom operators. In the absence of the latest and fastest networks, devices typically fall back to the previous generation of networks. Therefore, it is better that all of them are supported by the modem, although this is almost always the case.

Nutrition

As we have already mentioned, USB modems do not require separate power. Thanks to this, they can be used at any time; you just need to insert them into the USB connector of your computer.

Mobile routers run on batteries. The larger their volume, the longer the gadget will work. However, do not forget about such important battery consumption factors as working in 4G networks and the presence of additional sensors and functions.

Ethernet port

This is a connector that allows you to connect the modem to a computer using an Ethernet cable. This connection will ensure stable operation and the highest possible speed between the device and the modem. This function is only available on mobile routers, since USB modems are already connected to the computer.

Interface for external antenna

An external antenna is needed in order to better catch the network. After all, the signal can be unstable, especially outside the city; it depends on the time of day, weather and many other factors. The main disadvantage of the antenna is its low mobility. Therefore, this option is suitable only for those who have decided to set up a stationary Internet point, for example, in the country.

Additional functions

U mobile modems There are additional functions. But they may not be useful to everyone. In addition, many of them are quite energy-intensive. So decide right away which of the following you need.

Connector for MicroSD card useful for owners of laptops with a small number of USB connectors. By inserting a flash card into the modem, you can use it as a drive and, for example, store programs related to the Internet and connecting to it (to free up space on your computer and be able to immediately run everything necessary programs on another device by simply inserting the modem).

SMS service support allows you to use special program installed on your computer, receive and send SMS messages. This function is only available on USB modems.

Sensors and a display will help determine the charge level, the presence of networks, the number of connected users, etc. But you need to remember that with them the battery runs out faster.

An application for smartphones and tablets helps to monitor the charge level, connected users, and transfer data to the modem’s flash drive. This function is only available on mobile routers.

Dimensions

If we talk about USB modems, they are all no more than 100 mm in length and 40 g in weight. With mobile routers, everything is different. Their weight can reach 700 g, and dimensions – 250 x 100 mm. But there are also compact models that can be easily carried in your pocket.

Settings

For many users this will be an important parameter. After all, you want to launch the gadget and use it right away. Moreover, for many it will be a real problem to set up a modem - not everyone is fluent in technology. Therefore, based on this parameter, it is better to give preference to USB modems, and the simplest ones at that.

Criterias of choice

We looked at the main parameters of mobile modems and found out that the selection of characteristics depends on the needs of the user. You need to determine where and with what devices the modem will be used, as well as what additional functions will be needed. Based on user needs, we classified mobile modems.

For use in the city with a desktop computer worth purchasing

The Internet has taken over everything modern society. There are no longer any places in the world where there is no possibility of using it. There is a personal computer and laptop in every home. Computer skills are a mandatory requirement when applying for a job. Even printed products (newspapers and magazines) fade into the background, giving way to news portals online. Most Internet users have heard of modems. Many people have had to use them. But not everyone knows about the types of modems and the principles of their operation.

Modem and its functions

The main function of the modem is to ensure communication between devices during data exchange. If we talk in simple words, then this device is designed to encode, transmit, receive and convert signals. The areas of application of such devices are very wide: they are used in civil and military communications. Among ordinary consumers, the most popular are modems, which are used to provide an Internet connection. Let's take a look at how they work.

The most popular among users are modems that provide Internet access.

How the modem works

Initially, such devices were used to create computer networks using telephone lines. All information processed in computers is in digital form, and is transmitted via telephone cable in the form of an analog signal. Therefore, devices were needed that could connect PCs at different ends of the line.

The word "modem" is a derived form of "modulator-demodulator". Before transmitting data, it transforms the signal into a form that meets the requirements of the communication channel used (it modulates the signal), and changes the received signal into a form suitable for processing by the user’s computer (it demodulates the signal).

The modem is used to transform the signal into a form suitable for processing by a computer

History of the device

Digital modems arose from the need to transmit data between air defense units in North America. Mass production of modems in the United States began in 1958, primarily for the Sage air defense system (the first time the term "modem" was used). The devices were used in networks connecting terminals at various air bases, radar sites and command and control centers scattered throughout the United States and Canada.

The first representative of Bell Dataphone 103 devices was released in 1958, its data transfer speed was 300 bps. The AT&T telephone company introduced dataphone service (the company provided information transmission via telephone channels). The Bell 212a modem, released later, allowed data transmission at a speed of 1200 bps, but it was characterized by increased sensitivity to telephone line noise. The modem developed by Racal-Vadic turned out to be more resistant to noise. From that moment on, competition began for standards and rights in this industry.

The modem is used to transform an analog signal into a digital one

Modems have become widespread since 1977, when Dennis Hayes and Dale Hethertington released the 80-103A model. By the mid-2000s, modems became part of the computer, helping it turn into a multifunctional device that provides the user with the opportunity to receive information from around the world. Modems made individual computers parts of a global network.

Types of computer modems

Internet technologies have undergone significant development. The telephone cable can no longer cope with the required volume of data transfer. New types of modems have appeared with various functions and with different ways connections. A huge number of devices are produced, differing in areas of application and operating modes.

Any classification for modems can only be a conditional division. First of all, you need to determine what the modem is for. There are devices that provide work on a desktop computer, providing access to the Internet for all devices using Wi-Fi networks, and compact portable models that can provide Internet access anywhere with network coverage.

By method of execution

Depending on the methods of application and their operating conditions, modems are used, which can be divided into separate groups:

• external - are stand-alone devices that can be connected to a computer and other equipment;

  An external modem that receives power from the in-house electrical network

• internal - are, in fact, an expansion board;

  The internal modem is an expansion card installed in the computer

• built-in - are the internal part of devices such as a laptop or computer. These modems cannot be removed, they can only be disabled;

  The built-in modem is an integral part of the device

• Portable modems are designed for use with mobile devices. Their distinguishing feature- small dimensions, but at the same time full functionality, not inferior to other types of modems;

  Portable modems are used to provide mobile Internet access

• group - a set of individual modems assembled into a unit with a common power supply and control device. Refers to professional modems.

  Group modems are classified as professional modems

It must be remembered that internal modems are an integral part of devices, and built-in modems are installed as additional equipment.

By connection

Based on the connection method, modems can be divided into three categories:

• modems connected to USB, COM or Ethernet ports of a computer. These include devices with an external connection method;
• devices installed inside the computer in one of the PCMCIA, PCI, ISA slots;
• modems that are structurally part of other devices.

By type of supported networks

Depending on the type of networks in which they are used, they are produced different kinds modems. They can be divided into several categories.

Previously, modems were most often used to provide communication via telephone cables. Now, due to the development of wireless methods for connecting computers, compact USB modems are the most popular. With their help, high device mobility is achieved. Sales of such products on world markets are constantly growing. The majority of modems (82%) used by owners of laptops, computers and various mobile devices are modems connected to USB ports.

Table: types of modems by type of supported networks

Peculiarities
Analog	Used to connect to regular telephone lines, eliminating parallel use of the Internet and telephone communication
DSL	Used in a regular telephone network: unlike analogue ones, they allow simultaneous use of the telephone and the Internet
ISDN	Allows you to take advantage of the benefits provided by digital lines telephone communications, and allow you to achieve data transfer rates of up to 128 Kbps
DOCSIS, EuroDOCSIS	Used to gain access to the Internet on cable television networks
PLC	Used to transmit data via electrical network wires (internal house wiring 220 volts)
2G, 3G, 4G	Used in cellular systems communications
TNC	Used in packet radio networks
ZigBee	Used in local radio networks

Popular modem manufacturers

Since 2009, Chinese firms have played the leading roles in the modem manufacturer market. Huawei occupies 45% of the global USB modem market, while its competitor ZTE has 21%.

The list of device manufacturers is very large. The most popular now are:

• Zyxel;
• D-Link;
• USRobotics;
• Acorp;
• Tenda;
• Cisco.

The range of modems is constantly expanding:

recently appeared on the market the new kind modems. They help provide Internet access to all surrounding devices that can use Wi-Fi networks. Such a device is the Mi-Fi model manufactured by Novatel;

The Mi-Fi modem performs the functions of a portable (mobile) router

modems are no less popular ZyXEL Keenetic DSL. They provide a standard Internet connection using wires and allow you to set up a Wi-Fi network, which provides Internet access to all home devices. Convenient for use both at home and in the office;

The ZyXEL Keenetic DSL modem will provide Internet access to all devices in your home Wi-Fi networks

Particular attention can be paid to the ASUS DSL-AC52U model. It provides support for all mobile operators. The use of the device guarantees uninterrupted access to the Internet, which is achieved due to the ability to automatically switch between different networks;

The ASUS DSL-AC52U modem guarantees Internet availability due to the ability to switch between operators

Constant access to the Internet will be provided by the compact and convenient Huawei E3372h;

The Huawei E3372h modem will provide Internet access within the coverage area of ​​the mobile operator

Selecting, connecting and setting up an ADSL modem

Most often when connected to telephone networks ADSL modems are used.

The cheapest connection option is a modem equipped with a USB interface. Such devices are small in size and easy to set up. Unfortunately, not all computers are compatible with such modems.

Modem with USB interface is easy to use

Modems equipped with an Ethernet port are universal and connect to all computers and laptops. If you intend to use a desktop computer, and there is no need to create an internal Wi-Fi network, it makes sense to choose such a device.

Modems with Wi-Fi are the most popular. They provide for connecting devices both wired and wireless. Such a modem can work as a bridge or router. It provides Internet distribution via Wi-Fi network. Exactly like this multifunctional devices worth choosing to use. Main criterion estimates when choosing them are the power you need. The price of the modem and the range of the Wi-Fi signal depend on it. Accordingly, for small rooms a cheaper option will suffice; in case of requirements for covering a large area, it is necessary to choose a higher power.

A Wi-Fi modem will help you create a home network

To configure such devices, information from the provider is required - DNS and IP address, PVC, login and password assigned to the subscriber. These parameters are entered manually. Many operators provide a disk with necessary settings. In such cases, special knowledge and skills are not required to configure the modem.

If the modem has been used before, the best solution It will reset its settings to factory settings. This function is mainly used when changing providers or in case of losing the access password.

To return the settings to the default ones:

1. Connect the ADSL modem to a power source.
2. Find a button or hole (depending on the model) labeled Reset on the modem body.
3. Press the button for about 30 seconds.
4. If a hole is provided in the device for these purposes, you need to insert a thin metal object such as a paper clip into it and hold it there for some time.

If the manipulations are performed correctly, the device will reboot and return to factory settings.

Directly connecting the modem is done in the following way:

1. Connect the modem to the power supply.
2. Connect the telephone cable to the modem.
3. Connect the Internet cable leading to the computer to the LAN connector.
4. If the modem can distribute Wi-Fi, and your device is equipped with a Wi-Fi receiver, you do not need to connect the cable. Find the network on your device and enter the password specified in the instructions for the modem.
5. At correct connection The network indicator that the modems are equipped with should blink.

Setting up a modem usually does not raise questions even for the most inexperienced users, if there is installation disk. Everything happens automatically.

Video: how to set up an ADSL modem

Selecting, connecting and setting up a 4G modem

There are a number important indicators, which you need to pay attention to:

• the speed with which information is processed and received;
• presence of a slot for connecting an external antenna, power of the internal antenna;
• the number of consumers who can simultaneously connect to the modem;
• models of modem-compatible routers;
• the ability to automatically switch between different networks.

The most popular are 4G modems with a USB interface. They are convenient due to their versatility; they can be used with any device: tablets, laptops, computers with operating systems Windows systems 7, 8, 10 or Android. Comparison of technical characteristics will help to make right choice devices. It is advisable to choose a modem that has a warranty and an official service center. You need to purchase the device from trusted sellers.

Installing and configuring a modem is usually not difficult; the system carries out all actions in automatically. Let's consider connecting the modem to the Megafon 4G router:

1. Insert the modem with the SIM card into a free USB port on your computer or laptop.

   The modem must be inserted into a free USB port

2. After the system detects the device connection and opens the autorun window, click on “Run”.

   In the autorun window that opens, click “Run”

3. After this, the process of preparing the driver installation will begin.

   You need to wait until the preparation process for installing drivers is completed

4. Click the install button in the Megafon Internet window.

   To begin installing the modem software, click the “Install” button

5. Wait for the process to complete.

   Wait until the modem software is installed

6. After installation is complete, the system will notify you that a network has been detected.
7. Will happen automatic start programs. In the window that opens, click the “Connect” button.

   In the window that opens, click the “Connect” button

8. If you successfully connect to the Internet, the “Disconnect” item is activated in the “Modem” section.

   In the “Mode” parameter, select “Automatic selection”

9. The “Statistics” tab will help you monitor the speed of sending and receiving data, and control the remainder of the allocated traffic.
   

   Using the “Statistics” tab, you can control the data transfer speed and the remaining allocated traffic

Does Internet speed depend on the modem?

In reality, the speed of the device depends on the capabilities of the provider. However, each modem model has its own throughput, which also has a strong impact on this indicator. Estimated throughput capacities are usually indicated in accompanying documents to the equipment.

But we shouldn’t forget about factors such as the number of end consumers using the Internet or system load various programs running in the background. In addition, providers do not always provide the declared indicators. Don’t forget to timely optimize your system, update your antivirus software, and periodically clean your computer with utilities such as Glary Utilities.

Of all the variety existing types and types, the most interesting for ordinary users are modems that provide wireless access to the Internet from anywhere in the signal coverage area. As the capabilities of cellular operators grow, this method of connecting to the network is gaining popularity. Soon the speed wireless internet equals the capabilities provided by high-speed cable connections.

When connecting your laptop for the first time or personal computer When it comes to the Internet, poorly versed users usually have the question: “What are modems and why are they needed?” Within the framework of this article, a classification of modems will be given, and an algorithm for their installation and configuration will also be indicated, following which, without much difficulty, a novice computer specialist will be able to select and make such a device work.

What it is?

First, let's figure out what modems are. This is a special component in a computer that is designed to connect it to the The word “modem” was formed by combining two terms. The first of them is a modulator. This is the name in electronics for a special circuit that encodes a signal. And the second is a demodulator. That is, a device that does the opposite of the modulator. One of them encodes and transmits the signal, and the second receives and converts. Thus, until recently, most personal computers were connected to the Internet using telephone wires. Now the situation has changed, and they are slowly being squeezed out of this market segment network cards. They have higher speeds, and most motherboards are equipped with them. But there are still wireless modems that do not yet have a real alternative.

When are they needed?

Now let's figure out in what cases they are needed. Essentially, there can be three such moments. The first of them is now slowly becoming a thing of the past. It consists in the fact that a personal computer is connected to the Internet using such a device and a telephone line. Now it has been replaced by network cards. And the cost is lower, and the speed is several times higher. And the reliability of the connection in this case is much better. But for the Client-Bank system such a device is simply mandatory (second case). With its help, the accountant connects to the server of the financial institution. Without leaving the office, he can make a money transfer or check the availability of funds in the account. High speed in this case is not required. But connection protection is needed at the proper level. Now many organizations work with banks in exactly this format. The last case when modems are in demand is if a person travels a lot. He needs wireless connection to the Internet. In this case, the question is: “What are modems, and why are they needed?” - arises by itself. With the help of others technical means this issue simply cannot be resolved.

By method of execution

According to the method of execution, such devices are divided into two types: internal (that is, installed inside system unit computer) and external (to connect such a device, use the expansion slot of a computer, laptop or tablet). For the latter, you need to set the hardware toggle switch (if there is one) to the appropriate position. In this case, the following question must arise: “What is modem mode?” They can be digital or analog - determined by the telephone line signal. Only the first of them is available. All cellular networks work only in this standard. Therefore, such a switch is not provided for wireless devices. One more point needs to be noted. On old motherboards there were integrated (that is, soldered-in) similar devices. But now you can no longer find them on new personal computers.

By connection

The second classification, which has become widespread today, is based on the connection method. In accordance with it, these devices are divided into wired and wireless. In the first case, a special connector is provided into which the telephone wire is installed. In older devices, you could either talk on the phone or surf the Internet. Now there is a special modification of such devices. It allows you to simultaneously surf the Internet and communicate via telephone set. A special converter that separates the conversation and the transmitted signal into different frequencies. As a result, two data streams are transmitted over the same cable. In the second case, data transmission is provided by electromagnetic radiation without wires.

By type of supported networks

This parameter classifies only wireless devices. In accordance with it, they come in the following types: GSM (they are also sometimes called 2G), 3G and LTE (another name for 4G). All of them are backward compatible with each other. That is, 3G can easily work in GSM networks. Also, users are puzzled by what a USB modem is. It is in this form factor that most of these devices are made. By appearance is a flash drive that provides wireless transmission data. It is required to be equipped with a slot for installing a SIM card. It is connected to the rectangular USB connector of a personal computer.

Manufacturers

Conventionally, manufacturers of such equipment can be divided into two classes. The first of them is inexpensive and little-known trade marks, which include Sierra (their price starts from 180 rubles) and Sprint (the cost of such devices is 120-150 rubles). But the second class is more popular and high-quality devices. They are sold under the Pantech and Huawei brands. The price for them is already 600 rubles or more. But this is true for wireless devices. At the same time, the question often arises about what a 3G modem is. This is a miniature device (very similar to a flash drive in appearance), into which a SIM card of a mobile operator is installed, and with the help of it, data exchange with the Internet is ensured. In turn, among wired devices, the leading positions are occupied by D-Link and A-Corp. It is recommended to pay attention to them when purchasing such a device. The price for some models in this segment starts from 120 rubles. Moreover, their quality is impeccable.

Settings

Let's consider the order. These are all devices of this class, without exception: both wired and wireless. So, the setup order:

• Connection. For external ones, this means installing them in the expansion slot of a computing device. But when installing such an internal device, you need to remove the side covers of the system unit of the personal computer, install the board in the expansion slot, fix it and put everything back together.
• Installing drivers. In most cases, it occurs automatically, and user participation in this process is minimized. At the end, a message indicating the successful installation of this software should appear. (If this does not happen, they must be installed manually from a CD or from a website.)
• Next we connect to the Internet.
• At the final stage, launch the browser and check the functionality of the connection.

In some cases, you need to adjust the settings of the device (for example, change the analog dialing method to digital). This information is clarified with your provider and telephone operator.

Summary

This article answered the question of what modems are and why they are needed. Possible versions of such devices are given. Their operating modes and others are indicated specifications. A configuration algorithm is also given, following which you can easily and simply configure such a device for connecting to a computer network.