Safety guard system of video monitor system is a very important part of, is a kind of advanced, with strong ability of computer application technology combined protection of integrated technology system. We can through the remote cameras and related equipment, understand and grasp the dynamic monitoring site directly; Can monitor the scene of the image information, voice signal is sent to the control center in time, make the monitored area condition be clear at a glance, these, response speed and maximum alert to prevent crime has played a positive role in promoting. At the same time, the video monitoring system can run and anti-theft alarm system linkage, the ability to prevent more powerful. In recent years, because of multimedia application technology and the rapid development of computer image text processing technology, make the video monitoring system in such aspects as automatic tracking, real-time processing more had great development, so that the video monitoring system in the whole security guard has the pivotal status in the system. More and more widely application field. Now we go into stores, schools, streets or public places will see cameras for security purpose. Another characteristic of video monitoring system is that it can through digital hard disk video recorder to dynamic monitoring area of image and sound and complete real-time records, thus for future public security forensics, the case analysis provided valuable first-hand information. In short, video monitoring system has become an indispensable technical prevention system of the whole security is an important part.

Video surveillance system is mainly composed of camera (and sometimes pickup device), source transmission, control, display and power supply five major components.

Part one, the camera

It is the front end of the video monitoring system equipment, it is the "eyes" of the whole system. It is decorated in the monitored the alert area, in order to reduce the amount of the use of video cameras, optimization of transmission control and display system, we can be equipped with automatic zoom lens with precast yuntai camera, can automatically or people to control the rotation of the camera haeundae, make the camera for farther, the scope of the larger, intake of image more clear. Camera part is the system of the original signal. As a result, the stand or fall of camera part and it produces the image signal quality will directly affect the quality of the whole system. In terms of system noise calculation theory, the influence of system noise is one of the biggest factors in the system the first level of output, here is the camera image signals output SNR situation. So careful and scientific selection and processing of the video part is very important. Camera output image signal through the transmission part and control part to monitor, this process can reduce the signal-to-noise ratio of the image signal, the main reason of the problem is, transmission and control part of the circuit, amplifier, switches, etc. And because of the noise is introduced. The signal-to-noise ratio of the output video monitoring system can approximate calculation:

1) the first instruction in the camera found the output SNR performance indicators.

2) determine the noise coefficient of transmission system

If you don't have any amplifying device in transmission system, we can use the noise generator direct measurement noise factor.

If you have amplification device in transmission system, we must find out 1 and 2 respectively amplifier components of noise coefficient (available directly by amplifier performance indicators), and then sum get noise coefficient of the system.

3) the signal-to-noise ratio of the whole system is obtained

Can subtract from the camera to the output SNR transmission system to monitor all kinds of noise at the input coefficient is obtained.

* under the standard intensity of illumination of the camera, video monitoring system and technical indexes of image quality should satisfy:

Video signal output range: 1 vp - p + / - 3 dB

A black and white TV horizontal definition: 350 or more lines

Color TV level definition: 300 or more lines

Grey scale: 8 or higher level

10 db SNR: p

* in the case of poor environmental conditions, technical indexes and the image quality of the whole system should satisfy:

Video signal output range: 1 vp - p + 6 dB

A black and white TV horizontal definition: 300 or more lines

Color TV level definition: 250 or more lines

Gray levels: level 7 or higher

Signal to noise ratio: p 36 db

* under the condition of the normal work of the camera system, video monitoring system image quality should not be below the requirements for the level 4 in the table below.

 second, source transmission parts

It is the way of video surveillance system to spread information, it is not only the main transmission image, but also can be transmitted voice and video control signals. It is all to form the sum of the transmission system of transmission signal. Transmission part is the content of the main transmission image signal, so the research of image signal transmission mode and related problems in transmission is very important. Of image signal transmission, the key requirement is that after the image signal through the transmission system, does not produce obvious noise and distortion (chroma and luminance signal does not produce significant distortion), to ensure that the output from the camera image signal definition and grey level no obvious decline. This requires a transmission system in the aspect of noise attenuation, introducing and amplitude-frequency characteristic and phase frequency characteristics has good performance. In the mode of transmission, generally USES video baseband transmission mode. If the camera distance control center far away, also can use radio frequency transmission mode or optical fiber transmission way.

Third, control department

It is a video monitoring system of the central nervous, it is the system realize the function of command and dispatch center. Control part in control center, it is mainly composed of the console, the console generally fitted with digital hard disk video recorder, video matrix, image segmentation, video signal amplifier, the camera haeundae controller or keyboard, audio amplification device, microphone, audio controller (mic), active speakers and printing equipment, etc. Through these equipment can realize the front-end image signal, the audio signal and control signal extraction and amplification, switching and distribution, calibration and compensation, storing and printing. In addition, also can be installed on the console clock information display screen and LED display. Can install alarm controller and linkage control equipment, etc.

Part four, display

Generally consists of several or more monitors. It is the image information terminal display device. Display part in control center. For using digital hard disk video recorder for distribution of image information, image segmentation, and remote control front camera haeundae small video monitoring system, the monitor can be installed TV wall, also can be installed directly on the console. For a large video monitoring system, many sets of different size of the monitor can be installed on the TV wall, distribution of image signal by video matrix, picture by picture distributor switch and segmentation, by digital hard disk video recorder to record and storage.

Part five, the power supply

Due to the particularity of the safety system, emphasis should be placed on the power supply part of the work to ensure system was reliable, uninterrupted and safe operation. So generally require the use of focused, dedicated, independent power supply mode. For large video monitoring system also requires equipped with uninterruptible power supply or power systems.