Full color TV signal, analog TV is a collection of three signals: a video signal carrying information about the brightness of the image, a colour subcarrier with coded color information of the image and audio signal. Each of these signals for transmission on the distance uses its carrier frequency, which is determined by the specific standard television broadcasting and the channel number is used. The difference of carrier frequencies of video and audio is strictly standardized in every country and depends on used channel number broadcast. Russia has adopted an analog broadcast standard, providing a fixed difference carrying video and audio signal at 6.5 MHz. At an international conference in Stockholm in 1961 adopted the standards of television broadcasting systems, define the basic characteristics of the TV signal for each system. Each standard has A letter from A to M, which in combination with the standards applied by the decomposition and coding of color, completely describes the set of characteristics of analogue television systems around the world. Polarity modulation video signal is the standard that determines what level of signal is considered black and what is white. Depending on the broadcasting standard polarity can benegative” and “positive“. At negative polarity the maximum brightness corresponds to zero carrier level, when the positive — maximum. The first TV standards were used for positive modulation, however, this system had low noise immunity. Any impulse noise (such as from a car ignition) displayed as bright dots and lines, very noticeable. When the negative modulation of these interference are shown with black dots, much less noticeable. Therefore, the vast majority of today’s broadcasting standards provide for a negative polarity modulation. In Russia adopted a negative polarity. In the UK and France used in the 60-ies TV system with positive modulation, TVs contain a special circuit that allowed them to invert impulse noise to display them less noticeable black dots. The threshold inversion could change the special controller. If you select too low of a threshold light image can be displayed on the screen in the form of negativity.