July 10, 2023
I think they still remember accident on October 28, 2018, when a bus on Second Bridge over Yangtze River in Wanzhou, Chongqing, fell into river. A fight between passenger and driver caused bus to fall into river and all ten passengers were killed.
The blood lessons shocked whole country, but similar incidents still occur. Less than 3 months after this incident, a similar violent incident took place in Harbin. At around 4:23 pm on January 13, 2019, on bus No. 6 in suburbs of Harbin, a middle-aged man in a dark down jacket suddenly reached out and punched bus driver in face for missing a stop. . while cursing. Fortunately, driver reacted quickly and stopped in time, there were no serious consequences for cars and personnel.
On May 8, Songbei District People's Court of Harbin City held a public hearing on case that accused Lu Mou threatened public safety with dangerous means. Finally, defendant Lu Mou was sentenced to six years in prison for crime of endangering public safety.
While verdict has been passed and Lou has received his well-deserved punishment, we hope that this will not happen again. There is only one life, we must respect our life and their life too.
In addition, we would also like to thank for presence of video surveillance, which allowed us to directly see most real situation at time of incident. The surveillance announcement gave public an objective view and facilitated identification and sentencing of public security and justice officials. It is necessary to pay attention to normal operation of video surveillance.
In video surveillance, if there is a problem with image, in addition to a problem with surveillance equipment itself, it can also be a problem with cable or power supply.
What to do if monitoring interferes?
(1) Faults caused by cable impedance mismatch.
The expression is expressed as several vertical bars at same interval on monitor screen. The frequency of interference signal is basically an integer multiple of line frequency. This is due to an impedance mismatch caused by a video line impedance other than 75 ohms. The solution usually depends on method of "connecting resistance at beginning" or "connecting resistance at end in parallel". The best way is to find point of failure and deal with it carefully.
(2) Cosmic ray interference from cables.
If there is a lot of small or thick oblique moiré noise on screen, solution is to try to avoid or stay away from emitter at beginning of system; reinforce shielding, use steel pipes for cable conduits and ground them well, and if necessary, connect a video protection device. It is highly recommended that the system accept transmission over optical cable and this interference will no longer exist.
(3) Interference caused by poor cable quality.
The shielding of shield network is too low, or transmission resistance of main wire of video cable is too high to cause signal attenuation. Only after ruling out other possibilities and checking appearance of cable can it be considered as a bad video cable. To judge, one must take a sample of cable and submit it for inspection. If it is indeed a cable quality problem, all such cables must be replaced with materials that meet requirements in order to completely solve problem.
(4) Noise caused by excessive power ripple in power supply system.
The shape of expression is that a thick horizontal black bar slowly moves up and down in middle of image. There are many reasons why power supply ripples too much, for example: 1. Problem with filter capacitor 2. Interference signals are superimposed on normal power supply (50-period sine wave). controlled equipment very seriously pollutes power grid. The way out of this situation is relatively simple: entire system is powered by a cleaned power supply or online UPS, secondly, a qualified power supply is selected and a surge protector is installed.
