What is the difference between analogue, digital and cable television. Types of broadcasting: differences, advantages, disadvantages

Analogue television is a key stage of science, progress and technology. Previous discoveries allowed humanity to keep abreast of all important events. The invention of television made it possible to create a continuous flow of messages. Today, news and entertainment programs on television occupy 30% of human life. Science does not stand still, so progress allows us to improve not only the quality of transmitted communications, but also televisions.

History of televisions

Thanks to the scientist Smith, the photoelectric effect in selenium was discovered, which became the first step towards creating the television we are familiar with. Later, towards the end of the 19th century, the luminary of technical sciences Nipkow discovered the scanning disk to the whole world, which subsequently led to mechanical television. Before the discovery of television, many attempts were made to create something similar. Scientists from different countries worked on the creation of this smart device.

The 20th century saw attempts to transmit images over a distance. The first decade of the century was marked by the discovery of a receiver for broadcasting images.

Today humanity uses electronic television and radio broadcasting.

News without interruption

The American Ulysses Sanabria became the first who was able to transmit not only sound, but also image. This significant step took place in Chicago, at the television station WCFL.

For the first time, television broadcasts were introduced on a permanent basis in Germany. Naturally, it was broadcast in black and white. The Olympic Games in Germany were broadcast live.

Features of analogue and digital television

The component of television is the signal. Analog is supplied in continuous mode. Due to external factors (weather conditions), the signal may be worse, which affects the image quality. Analogue television has a significant advantage: the signal is received using a conventional antenna without additional equipment. Also, if desired, it is possible to connect cable television through a provider.

The disadvantage of an analog signal is the presence of a large amount of unnecessary information. With the advent of digital, demand for analog television fell by almost 100%.

Today, an analog signal is considered obsolete. It has been replaced by digital.

Most modern televisions are designed for the use of digital television, but the presence of an analog connector is still a mandatory criterion for selecting equipment. Many experts argue that an analog signal is not able to use modern plasmas with LCD screens to their full potential. The digital signal arrives partially intermittently, which ensures very high quality picture and sound transmission.

A big advantage is the ability of digital technologies to transmit a large number of broadcast channels for every taste, when analogue television channels will be tens or even hundreds of times smaller. Digital signals can restore outgoing data; they are transmitted in an encrypted code.

Differences between analogue and digital television

Unfortunately, analogue television has virtually no advantageous qualities compared to digital broadcasting. The only advantage that attracts many TV viewers is the use of a standard television antenna. Disabling analog television will cause a lot of inconvenience for many.

On the other hand, digital television can be tuned in thanks to a digital signal receiver. It should also be taken into account that digital always provides a guarantee of quality, and protection from interference and hackers leaves no chance for analogue television to remain at the peak of popularity. Although many continue to use this particular type of signal to watch television channels.

Comparative characteristics

• A digital signal makes it possible to obtain high quality transmitted images.
• The mobility of digital technologies allows you to receive signals while traveling or anywhere outside your home.
• An analog signal does not allow access to a wide range of channels.

Digital television: advantages and disadvantages

The main advantage is that digital provides a unique opportunity to obtain super-high quality image and sound. Modern television systems are equipped with new standards that provide high picture clarity.

Increased functionality of the equipment is considered a positive quality. Interactive television systems provide potential opportunities to influence the broadcast television program. The program has functions that allow you to start the broadcast from the beginning, turn on the video recording, transfer the video to the archive, or even turn on subtitles.

Some disadvantages should also be noted.

Digital television is limited to a certain coverage area. Only within this zone the reception and transmission of signals works flawlessly. If the signal level is insufficient, frames will freeze, or the picture will be scattered into square image systems. There is no average quality here, the signal arrives “excellently” or does not pass through at all.

Television in Russia

At the beginning of autumn, the Russian Broadcasting Network promises to provide a program according to which analogue television channels will be turned off. The program indicates the fact that if this type of signal is used in a region of no more than 5%, it is allowed to be turned off.

To date, analogue television in Russia has survived only in eight regions.

Many TV channels included in multiplex No. 2 have a great interest in turning off the analog signal, because they are required to pay for the distribution of both analog and digital television.

By and large, a successful transition from one type of signal to another depends only on the execution technique. The main task remains to determine a signal that is accessible to absolutely all families, so that after the transition to digital technologies, residents of remote regions will not be left without television broadcasting.

Features of broadcast television

Analog terrestrial television remains one of the most popular methods of transmitting television products. To transmit television and radio programs, high-frequency oscillations are used. Unlike low-frequency pulses, high-quality electrical vibrations can propagate in the form of radio waves throughout the surrounding space. Such over-the-air television signals are received through antennas, which allows you to receive the signal on televisions and watch programs. This method of transmitting and receiving television signals is called terrestrial or terrestrial. The frequency used to transmit signals is tuned strictly according to established standards.

Today, both analog and digital television are very popular among TV viewers and radio listeners. Who knows, maybe in a few years these transmission systems will become as outdated as all the previous ones. At least analog television is already fading into the background.

Signals are information codes that people use to convey messages in an information system. The signal can be given, but it is not necessary to receive it. Whereas a message can only be considered a signal (or a set of signals) that was received and decoded by the recipient (analog and digital signal).

One of the first methods of transmitting information without the participation of people or other living beings were signal fires. When danger arose, fires were lit sequentially from one post to another. Next, we will consider the method of transmitting information using electromagnetic signals and will dwell in detail on the topic analog and digital signal.

Any signal can be represented as a function that describes changes in its characteristics. This representation is convenient for studying radio engineering devices and systems. In addition to the signal in radio engineering, there is also noise, which is its alternative. Noise does not carry useful information and distorts the signal by interacting with it.

The concept itself makes it possible to abstract from specific physical quantities when considering phenomena related to the encoding and decoding of information. The mathematical model of the signal in research allows one to rely on the parameters of the time function.

Signal types

Signals based on the physical environment of the information carrier are divided into electrical, optical, acoustic and electromagnetic.

According to the setting method, the signal can be regular or irregular. A regular signal is represented as a deterministic function of time. An irregular signal in radio engineering is represented by a chaotic function of time and is analyzed by a probabilistic approach.

Signals, depending on the function that describes their parameters, can be analog or discrete. A discrete signal that has been quantized is called a digital signal.

Signal Processing

Analog and digital signals are processed and directed to transmit and receive information encoded in the signal. Once information is extracted, it can be used for various purposes. In special cases, information is formatted.

Analog signals are amplified, filtered, modulated, and demodulated. Digital data can also be subject to compression, detection, etc.

Analog signal

Our senses perceive all information entering them in analog form. For example, if we see a car passing by, we see its movement continuously. If our brain could receive information about its position once every 10 seconds, people would constantly get run over. But we can estimate distance much faster and this distance is clearly defined at each moment of time.

Absolutely the same thing happens with other information, we can evaluate the volume at any moment, feel the pressure our fingers exert on objects, etc. In other words, almost all information that can arise in nature is analogue. The easiest way to transmit such information is through analog signals, which are continuous and defined at any time.

To understand what an analog electrical signal looks like, you can imagine a graph that shows amplitude on the vertical axis and time on the horizontal axis. If we, for example, measure the change in temperature, then a continuous line will appear on the graph, displaying its value at each moment in time. To transmit such a signal using electric current, we need to compare the temperature value with the voltage value. So, for example, 35.342 degrees Celsius can be encoded as a voltage of 3.5342 V.

Analog signals used to be used in all types of communications. To avoid interference, such a signal must be amplified. The higher the noise level, that is, interference, the more the signal must be amplified so that it can be received without distortion. This method of signal processing spends a lot of energy generating heat. In this case, the amplified signal may itself cause interference for other communication channels.

Nowadays, analog signals are still used in television and radio, to convert the input signal in microphones. But in general, this type of signal is being replaced or replaced by digital signals everywhere.

Digital signal

A digital signal is represented by a sequence of digital values. The most commonly used signals today are binary digital signals, as they are used in binary electronics and are easier to encode.

Unlike the previous signal type, a digital signal has two values ​​“1” and “0”. If we remember our example with temperature measurement, then the signal will be generated differently. If the voltage supplied by the analog signal corresponds to the value of the measured temperature, then a certain number of voltage pulses will be supplied in the digital signal for each temperature value. The voltage pulse itself will be equal to “1”, and the absence of voltage will be “0”. The receiving equipment will decode the pulses and restore the original data.

Having imagined what a digital signal will look like on a graph, we will see that the transition from zero to maximum is abrupt. It is this feature that allows the receiving equipment to “see” the signal more clearly. If any interference occurs, it is easier for the receiver to decode the signal than with analog transmission.

However, it is impossible to restore a digital signal with a very high noise level, while it is still possible to “extract” information from an analog type with large distortion. This is due to the cliff effect. The essence of the effect is that digital signals can be transmitted over certain distances, and then simply stop. This effect occurs everywhere and is solved by simply regenerating the signal. Where the signal breaks, you need to insert a repeater or reduce the length of the communication line. The repeater does not amplify the signal, but recognizes its original form and produces an exact copy of it and can be used in any way in the circuit. Such signal repetition methods are actively used in network technologies.

Among other things, analog and digital signals also differ in the ability to encode and encrypt information. This is one of the reasons for the transition of mobile communications to digital.

Analog and digital signal and digital-to-analog conversion

We need to talk a little more about how analog information is transmitted over digital communication channels. Let's use examples again. As already mentioned, sound is an analog signal.

What happens in mobile phones that transmit information via digital channels

Sound entering the microphone undergoes analog-to-digital conversion (ADC). This process consists of 3 steps. Individual signal values ​​are taken at equal intervals of time, a process called sampling. According to Kotelnikov’s theorem on channel capacity, the frequency of taking these values ​​should be twice as high as the highest signal frequency. That is, if our channel has a frequency limit of 4 kHz, then the sampling frequency will be 8 kHz. Next, all selected signal values ​​are rounded or, in other words, quantized. The more levels created, the higher the accuracy of the reconstructed signal at the receiver. All values ​​are then converted into binary code, which is transmitted to the base station and then reaches the other party, which is the receiver. A digital-to-analog conversion (DAC) procedure takes place in the receiver's phone. This is a reverse procedure, the goal of which is to obtain a signal at the output that is as identical as possible to the original one. Next, the analog signal comes out in the form of sound from the phone speaker.

The average person doesn’t think about the nature of signals, but sometimes he does about the difference between analogue and digital broadcasting or formats. By default, it is believed that analog technologies are becoming a thing of the past, and will soon be completely replaced by digital ones. It’s worth knowing what we give up in favor of new trends.

Analog signal- a data signal described by continuous functions of time, that is, the amplitude of its oscillations can take any value within the maximum.

Digital signal- a data signal described by discrete functions of time, that is, the amplitude of oscillations takes only strictly defined values.

In practice, this allows us to say that an analog signal is accompanied by a large amount of noise, while a digital signal successfully filters it out. The latter is capable of restoring the original data. In addition, a continuous analog signal often carries a lot of unnecessary information, which leads to its redundancy - several digital signals can be transmitted instead of one analog signal.

If we talk about television, and it is this area that worries most consumers with its transition to “digital,” then we can consider the analog signal to be completely obsolete. However, for now, analog signals can be received by any equipment designed for this purpose, while digital signals require special equipment. True, with the spread of digital television, there are fewer and fewer analogue televisions and the demand for them is catastrophically decreasing.

Another important characteristic of a signal is security. In this regard, analog demonstrates complete defenselessness against outside influences or intrusions. The digital one is encrypted by assigning it a code from radio pulses, so that any interference is excluded. It is difficult to transmit digital signals over long distances, so a modulation-demodulation scheme is used.

Conclusions website

1. The analog signal is continuous, the digital signal is discrete.
2. When transmitting an analog signal, there is a higher risk of clogging the channel with interference.
3. The analog signal is redundant.
4. The digital signal filters out noise and restores the original data.
5. The digital signal is transmitted in encrypted form.
6. Multiple digital signals can be sent instead of one analog signal.

The difference between digital and analogue television is most easily illustrated by the differences between digital and analogue audio or photography. If in analog the television picture and sound track are encoded using an analog electrical signal, then in digital, accordingly, digital encoding is used.

At the end of the 90s, only analog color television existed in our country. The broadcast used the French SECAM coding system. Older readers probably remember that on video cassettes one could find films encoded using alternative systems - PAL or NTSC, for comfortable viewing of which a VCR with their support was needed.

To watch digital TV on a computer, all you need is a small USB module and a UHF antenna

The main disadvantages of the analogue are poor protection against interference, as well as a fairly wide band of the radio frequency spectrum required for transmitting one channel.

Therefore, on air we were limited to a maximum of two dozen color channels, and on cable networks an average of 70 (with rare exceptions).

If the TV is not equipped with a digital channel receiver, then you can buy a separate decoder that supports the DVB-T2 standard

With an analog signal, it is quite difficult to create a service convenient for the user and operator (with the ability to quickly connect/disconnect channel packages, etc.). In addition, analog needs high-power transmitters with a large coverage area because Receivers need a high signal level to get a good picture, which means that the frequency spectrum on the radio is used very irrationally: in neighboring territories it is impossible to transmit on the same channel, competent frequency planning is required.

A digital signal does not have these disadvantages. The main advantage of digital is that the encoded channel can be compressed using modern algorithms (for example MPEG). Exactly how to encode a signal and how to compress it is determined by the standard. Today in Europe and Russia the main family of standards is DVB - the brainchild of the international consortium DVB Project.

The family includes standards for satellite, terrestrial, cable and mobile television, differing in the degree of compression, noise immunity and other parameters (important, depending on the transmission medium used). However, in the press, “digital” has recently been most often referred to as the terrestrial standard (in the case of Russia - DVB-T2). Let's start with it.

From analog to digital on air: Russian version

Given the advantages of digital, the world community began the transition to modern broadcasting standards in the early 2000s. In all countries, this process went on (and continues to go on) simultaneously with the “optimization” of radio air, which is actively used not only by television broadcasters, but also by mobile operators, the military and other consumers.

Due to compression into 1 analogue television channel, for example, in the DVB-T2 standard, it allows you to fit up to 10 digital channels with approximately the same picture quality. In addition, part of the spectrum frees up the aforementioned reduction in transmitter power. Within one country, these processes are regulated by the state, and on a continental scale - by various interstate agreements.

According to one such agreement, Russian border areas must eventually stop broadcasting in analogue format. So the transition from analogue to digital television determines not only the desire for new technologies, but also responsibility to our closest neighbors.

Inexpensive USB adapters for receiving digital channels can be found not only for PCs...
...but also for smartphones and tablets. At the same time, they will be connected via micro-USB

The transition from analogue to digital television on air in our country began in 2009. At that time, the DVB-T standard, which had already been implemented in a number of European countries, was taken as the basis.

You need to understand that television is a chain of interaction between a whole list of intermediaries between the content producer and its consumer, each of whom has a fleet of analog equipment that needs to be replaced. The state project involves updating only part of this chain - distribution and transmission equipment.

In some cases, the state helps television studios purchase new filming equipment.

But viewers have to think about replacing the “receivers” themselves. All these difficulties do not allow us to suddenly switch to a new standard, no matter where such transformations are undertaken.

And in our country the transition was even more difficult. At first, a very high pace was taken, but after a few years, “the horses were changed in midstream”, saving time on the next evolutionary step: it was decided to introduce a more advanced second generation of the “terrestrial” standard - DVB-T2, which ensures the placement of a larger number of digital channels on the frequency analog channel bandwidth (compared to DVB-T).

It should be noted that the transition does not imply any increase in the resolution of the broadcast image. The project only involves changing the way it is presented, and we should expect HD quality on air only in the distant future (the standard supports HD, but at the state level it was decided not to touch this topic for now).

Today, DVB-T2 transmitters operate almost throughout the country. Somewhere, only 1 multiplex is currently included (a package that takes the place of one analog channel); in other areas the second one was already included. This means that, having the appropriate receiving equipment, you can watch 20 channels in decent quality from the air for free.

Although from the very beginning of the transition it was said that by 2015 our country should completely switch to digital and turn off analog, for now the issue of turning off was postponed, so analog television continues to function.

Photo: manufacturing companies

Digital television is rapidly gaining popularity in our country, but many people still do not know how it fundamentally differs from the good old analog TV.

Description

It is not difficult to guess that analogue and digital television are based respectively. The analog signal is continuous, which means that in the event of any external influence it becomes vulnerable, which leads to worse picture and sound quality. An undoubted advantage of an analog signal is the ability to receive it using a simple terrestrial antenna. You can also use the services of a cable TV provider. We can say that the analog signal today is already outdated, since it is significantly inferior to the digital signal in a number of important parameters - quality, safety, etc.

Modern TVs are designed primarily to work with digital signals, although they also have an analog connector. The whole point is that an analog signal is not capable of revealing the full potential of modern plasma and LCD TVs; only a digital signal can provide better picture quality. Unlike analog, it arrives in compact “portions” that are separated by pauses, and therefore it is very difficult to influence such a signal. Even when transmitting a digital signal over a very long distance, the quality of picture and sound remains at the highest level. Among other things, a digital signal allows you to transmit much more channels than an analogue one, so subscribers who connect to digital television receive more than a hundred TV channels on a wide variety of topics.

Comparison

Alas, analogue television today actually has no obvious advantages over digital broadcasting, except perhaps the ability to “catch” a signal using a conventional antenna. However, digital television can also be mobile using a digital signal receiver. Considering that, regardless of the distance, the digital signal remains protected from hacking and interference and guarantees a high level of quality, the advantages of digital television become completely obvious.

Conclusions website

1. Digital television provides a higher level of signal quality and protection. The analog signal was and remains vulnerable to external influences and cannot provide such high-quality images.
2. Digital television is more mobile - today you can receive a digital signal while on the road or far from home.
3. Analog television is not capable of providing as many channels as digital television. Due to the peculiarities of the digital signal, when connecting to digital TV, the subscriber can gain access to several hundred different TV channels.