Each of us faces daily electronic devices - it has already become a familiar mobile phone, a computer for work and leisure, TV, radio and so on. Ten years ago, no one thought much, digital or analog signal is used in a particular device.But it took a little time, and the term "digital" thanks to sophisticated advertising campaign began, many associated with the words "good quality, reliable."Admittedly, some truth in this.The analog signal is started to be used for transmission of information earlier than digital.This is due to its easy handling, the unwillingness of the infrastructure and some other reasons.
To understand what an analog signal, it is necessary to remember the basics of electrical engineering, in particular, the nature of electricity.After the signal in question is, in fact, directly connected with it - it can be a direct transfer of power, and by means of electromagnetic fields.Surely, the "famous" sinusoid heard everything.
Mentally draw a horizontal line - this is the time axis.It is strung like a continuous wavy line, the height of the waves, which are above and below the axis is.Next, imagine that we have this wavy line stretch along the time axis.As a result, decrease the number of waves relating to a time interval.And now the "squeeze" sine - wave began to go more often.In other words, these actions we change the frequency.If we continue the thought experiment and "shrink / stretch" of the wave up and down relative to the axis of time, thus it will be able to change the amplitude.It is formed and an analog signal.
radios used in these two ways - FM (Frequency Modulation) and AM (Amplitude Modulation).Of course, the above example is simplified for understanding.In addition to changing the frequency and (or) the amplitude of the wave exposed and the other, more specific changes.More about this can be found on specialized sites and in the literature.
Based on the above, we can formulate a definition: the analog signal is continuous in time modulation method of transmitting information.One of the disadvantages is susceptibility to "noise pollution".Now mobile phones are at all.And everyone, at least once, leaving the phone operating near the TV or computer speakers.Those strange ordered clicks distributes the speakers before receiving SMS or receiving a call, are known to all.They represent the electromagnetic interference, wedged into the reproduced sound of the TV or computer.Obviously, this is undesirable.
Aiming arises in conductors speakers.In fact, the transmitted modulated wave (analog signal) is subjected to external impact, it distorts.Of course, in this case, the person is easily identifies useful data (sound) from the noise, but if the signal is received by logic, there is a number of difficulties.For example, it is impossible to reliably determine where useful data, and where the noise.
Therefore, the analog transmission method has been replaced by digital.Analog and digital signal fundamentally different.The second is created as follows: Sine conditionally is divided into a set of points, the position of each encoded by a specific sequence of pulses and gaps (lack of power).Generally pulse corresponds to a logical unit, and the interval - zero (although it may be the opposite way).The receiver decodes the received pulses and restores the original sine wave.Obviously, such a signal is less subject to noise, since the decoding unit clearly distinguishes pulses.However, the excessive noise level digital signal is simply lost.
