Surveillance camera jamming solution
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Keywords : Surveillance camera jamming solution
1. Wood grain interference
The appearance of this kind of interference will not submerge the normal image when it is slight, and the image can not be watched (or even destroy the synchronization) in severe cases. This failure phenomenon is more complex and more reasons. Generally for the following reasons:
(1) the quality of video transmission line is not good, especially the poor shielding performance (shielded network is not a good quality copper wire mesh, or shielding network is too thin but not shielding effect). At the same time, this line of video line resistance is too large, resulting in a greater signal attenuation is also a cause of increased failure. In addition, the characteristic impedance of this type of video cable is not 75Ω and the parameter is out of specification is also one of the causes of failure. As the interference phenomenon is not necessarily the video line failure caused by poor, so the reason for this failure to determine when accurate and prudent. Only when the exclusion of other possible, from the perspective of poor video line to consider. If it is the cable quality, the best way of course, all of this cable all replaced, replaced with the cable to meet the requirements, which is the best way to solve the problem. In this case,
(2) because the power supply system is not "clean" caused. Here the power supply is not "clean", refers to the normal power supply (50 weeks of the sine wave) superimposed on the interference signal. And this power supply on the interference signal, and more from the use of the power grid in the SCR device. In particular, high current, high voltage thyristor equipment, power grid pollution is very serious, which led to the same power grid is not "clean." Such as the power grid in the high-power thyristor frequency control devices, SCR rectifier, SCR AC-DC converter, etc., will produce pollution to the power supply. The solution to this situation is relatively simple, as long as the entire system using clean power or online UPS power supply can basically be resolved.
(3) near the system there is a strong source of interference. This can be judged by investigation and understanding. If this is the case, the solution is to strengthen the camera's shield, as well as the video cable pipe grounding treatment. In this case,
2. Deep relatively messy large area moire interference
Serious when all the images were destroyed, not a form of images and synchronization signals, this failure is due to video cable lines and shielded wire short-circuit, caused by an open circuit. This is most often seen on BNC connectors or other types of video connectors. That is, this failure phenomenon occurs, often not the whole system of the various signals are problems, but only in those joints bad way on the number. As long as carefully check these connectors one by one, you can solve. In this case,
3. A number of vertical bars with equal spacing
The frequency of the interfering signal is essentially an integral multiple of the horizontal frequency, due to the impedance mismatch caused by the characteristic impedance of the video transmission line which is not 75 Ω. It can also be said that this interference is caused by the video cable's characteristic impedance and distribution parameters are not meet the requirements caused by a comprehensive. The solution method generally relies on "the beginning end series resistance" or "the terminal connects the resistance" the method to solve. In addition, it is worth noting that the video transmission distance is very short (usually within 150 meters), the use of the impedance mismatch and distribution parameters of the video cable is not necessarily the above-mentioned interference. The fundamental solution to these problems is to purchase video cable, be sure to ensure quality. The cable should be sampled as necessary.