Coaxial cable use and distinguish function
Coaxial cable is a layer of insulated wire wrapped around the central copper conductor cable. Coaxial cable is characterized by good anti-interference ability, stable transmission of data, the price is cheap, the same is widely used, such as closed-circuit television lines.
When the signal is transmitted in the coaxial cable, its attenuation is related to the transmission distance and the frequency of the signal itself. In general, the higher the signal frequency, the greater the attenuation. The video signal has a large bandwidth of 6MHz, and the color part of the image is modulated at the high end of the frequency, so that when the video signal is transmitted in the coaxial cable, not only the overall amplitude of the signal is attenuated, but also the attenuation of each frequency component is very different , Especially the color part of the largest attenuation. Therefore, the coaxial cable is only suitable for close transmission of image signals, when the transmission distance of 200 meters or so, the image quality will be significantly reduced, especially the color becomes dim, there is distortion.
The coaxial cable has a certain amplification of the video signal, and can also be adjusted by equalization of different frequency components were different size of the compensation, so that the output of the video signal output distortion as small as possible. However, the coaxial cable can not be unrestricted cascade, generally in a point to point system it can only cascade up to 2 to 3, or can not guarantee the quality of video transmission, and adjust it is also very difficult.
In addition, the coaxial cable in the monitoring system to transfer image signals there are some shortcomings:
1. It itself is affected by climate change, the image quality is affected.
2. It coarser, in intensive monitoring applications wiring is not convenient.
3. Can only pass video signals, if the system needs to transmit control data, audio and other signals, you need another wiring.
4. Coaxial cable anti-interference ability is limited, can not be applied to strong interference environment.
5. Also has the difficulty of adjusting the shortcomings.