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"It'll be a beat."
I believe that this dialogue is a lot of childhood memories after 80's and 90's. Every time I watch TV at home, there is a screen display failure. Adults often cook a meal. Of course, in light of this kind of simple and crude practice, there is still a principle that can be justified. After all, in that age when technology was lagging behind, the working principle of high-end electronic devices such as television was magical and strange to many families. But unlike clumsy appliances such as diode TVs in the past, today's home appliances are often designed to be precise, and the principle is responsible. Taking a beat of the treatment will only aggravate the damage, especially the monitor equipment in the video surveillance system. 
The monitor is often very easy to display because of long-term video monitoring screens, and there are display problems such as snowflakes, bars and the like. However, the focus of many problems is not the damage of the monitor itself. So how do we deal with these problems?
1. A black bar or white bar appears on the monitor screen and scrolls up or down, which is the so-called 50 Hz power frequency interference. This type of interference is caused by the potential difference between the front-end and the control center, which causes potential difference loops to enter the video surveillance system. It is also possible that the power supply performance of the device itself will be reduced.
2, the video surveillance image has snow noise, this type of interference is mainly caused by signal attenuation on the transmission line and coupled with high-frequency interference.
3, video surveillance images have ghosting, or the image is whitish, character jitter, or on the monitor screen to produce a number of equal spacing of the vertical bar interference. This is because the characteristic impedance between the video surveillance transmission line or the equipment is not 75Ω, resulting in impedance mismatch.
4, twill interference, beating interference, power interference. When this interference is slight, it does not overwhelm the normal image, but when it is severe, the image is distorted and cannot be viewed. The reason for this is more and more complicated. For example, the quality of the video transmission line is not good, especially the shielding performance is poor, or the power supply system has clutter, or there may be a strong interference source near the video monitoring system.
5, large area moire interference, also known as single-frequency interference. This phenomenon is mainly caused by the short circuit caused by the short-circuit of the video cable's core wire and the shield, or the failure caused by the open circuit, or due to the bad contact of the BNC connector.
Serious Teaching Lesson 30: Video Surveillance Images Can Be Cured Without Beating
"What about the snow on the TV screen?"