Pull Down Stainsteel Steel Kitchen Faucet Heshan Dingquan Sanitary Ware Industry Co., Ltd , https://www.dqoksanitary.com
Type dynamic amplification
Dynamic amplifying anti-jamming device, which is effective for some distances or bad lines, and some more slightly strong electricity, elevator interference
<br> <br> frequency shift frequency shift jamming devices, some of the strong electrical interference, radio, power plants, elevators interfere with work <br> <br> interference is how to generate:
Coaxial cable, whether it has one layer, two layers or four shield layers, is a coaxial outer conductor shielding layer which is electrically connected to each other, but it is only different in specific structure and thickness. In practical engineering applications, interference sources mainly include fluorescent lamp interference, elevator interference, strong electrical interference, power generation equipment, frequency conversion equipment, and radio transmission equipment interference. Camera output video amplitude Vo=2Vp-p, output impedance is 75Ω, coaxial cable inner conductor The equivalent impedance is Rc, and the equivalent impedance of the outer conductor is Rd. Vi is the induced electromotive force (the magnitude is proportional to Rd, strictly proportional to the longitudinal reactance Zd) formed by the disturbance on the longitudinal impedance of the coaxial outer conductor. The end device is for the transmission line. It is a Rh=75Ω matching load. Obviously, the signal voltage obtained by the terminal load Rh from the transmission loop is the result of the combined effect of the video signal Vo and the interference electromotive force Vi.
Vab=(Vo×75)÷[75×2+Rc+Rd]]+(Vi×75)÷[75×2+Rc+Rd]]
Among them, the first item is the effective video signal obtained by the load, Voh=(Vo×75)÷[75×2+Rc+Rd]],
The second item is the effective interference signal obtained by the load, Vih=(Vi×75)÷[75×2+Rc+Rd]]. When the cable is very short, the resistance of the inner and outer conductors can be neglected. Rc+Rd=0. The effective video signal Voh=(Vo×75)÷75×2+0)=Vo×75÷75×2=Vo/2=1 Vp-p; because the interference-induced electromotive force Vi is proportional to (Rc+Rd), Vi = 0, Vih = 0; it is worth noting that the interference signal Vi is determined by the cable longitudinal distribution parameters (impedance or resistance), not a concentrated point source, it is important that it is connected in series in the video signal transmission loop, the load When the camera video signal is obtained, it is also necessary to obtain the interference signal. The nature of the interference is "additive interference" and it is always present regardless of the presence or absence of video signals.
Interference mask
Elevator interference solution:
The main causes of video interference in elevators have been analyzed in detail above. As long as the causes of interference are identified, the interference problem can be solved. To solve the elevator interference should mainly start with the following points:
1. Select a video cable with small attenuation coefficient, good shielding performance, and high tensile strength, so that it can improve its anti-interference ability and reduce video attenuation.
2. Reasonable wiring: Reasonable wiring can effectively avoid the interference signal being “coupled†by the cable, minimize the parallel bundle distance with other cables, and keep the video cable away from interference.
3. Power supply interference is also an important source of interference for video signals. Therefore, it is necessary to use a small ripple power supply to prevent power supply interference or to use centralized power supply in the equipment room to avoid power interference. If you can not determine where the interference signal is introduced into the system, first determine whether it is power interference, find a battery, and directly supply power to the camera. If the interference is eliminated, it is proved to be power interference. If it cannot be excluded, it is proved to be intrusive interference in the transmission cable.
What is a video anti-jamming device
The video anti-jamming device is the best auxiliary tool to solve the video interference problem in video surveillance. At present, there are mainly two methods for my anti-jamming device, one is the frequency-shift anti-jamming method, which can completely solve the interference; the other is the amplification anti-jamming method. In principle, this kind of anti-jamming device does not Can not eliminate the interference, but it can effectively reduce the amplitude of the interference signal. Assuming that the output amplitude of the video signal is U1 and the amplitude of the interference signal is U2, the amplitude of the video signal arriving at the terminal is the sum of the source signal and the interference signal, that is, U1+U2 (without considering the attenuation of the signal itself), and the amplitude is U2's interference signals cause serious interference with the image displayed on the monitor screen. If the front-end original video signal is transmitted, an amplifier is used to first magnify the amplitude by n times to Nu1. After the transmission is performed, the U2 interference signal is also mixed. After reaching the terminal, the signal becomes NU1+U2, which is obviously higher than the amplitude. The input level requirement of the display device is allowed. Therefore, an attenuator is also required to attenuate the combined signal of the mixed interference signal received at the terminal by n times to obtain (nU1+U2)/n=U1+U2/n. The signal amplitude at the point of recovery is U1, and the interference component becomes U2/n. It can be seen that after the signal is first amplified and then compressed, the video signal output to the display device can still maintain the original amplitude, and the interference signal amplitude is reduced by n times. This means that, from the monitor screen alone, the original strong interference will be weaker, and the original less powerful interference will be insignificant.