How to choose the transmitter in security monitoring system?
APL, that is, the average image level, many engineers are not too careful or not too familiar with this indicator. However, if such a problem encountered in Engineering: when it comes to some video signal through the optical transmission, when a large area of white in the picture (such as camera glare screen) will monitor the level of jitter, so engineers must not strange. This is because the voop some manufacturers of the APL range is too narrow, when there is a large area of white in the image signal, the DC component of each line in the image signal increases, APL will increase, causing the line sync signal amplitude decreased or lost, the monitor cannot detect the line synchronization and screen jitter. If you need to buy otical if the Pacific security network, recommend a few brands pdh.
Video bandwidth is an old growth issue. The video bandwidth is not enough, the detail of the monitor screen is not clear enough, the horizontal resolution is low, and even the color distortion or video loss is serious. Because of the importance of video bandwidth for image quality, some unscrupulous vendors intentionally exaggerate the video bandwidth of the product to deceive customers. For example, a digital video optical transceiver manufacturers claim their video bandwidth is 8M, but the release of video sampling frequency is 12.5M. According to Nyquist's law of sampling, the signal should be sampled at least two times as much as the signal frequency. So now, the transmitter manufacturers the theory of video bandwidth in any case can not be more than 6.25M. Obviously, this is a lie to exaggerate the quality of cheating customers, so that no business reputation vendors should not consider the scope of the purchase. But not all customers can accurately identify vendors lie, for general contractors and users, by observing the details of the image, you can rough judgment of the device's video bandwidth.
Multichannel digital video optical multiplexer can have a variety of functions, each function have corresponding technical parameters, such as video, audio, data index index index index, Ethernet, asynchronous call index etc.. Specific technical indicators may require manufacturers to provide the third party testing proves that the conditional project should be provided before buying equipment according to the manufacturer's index of retest, in order to test the actual equipment technical indicators and the integrity of the manufacturers. Here from the engineering point of view, simply explain the following two video indicators.
