The video monitoring system is generally composed of four main parts: front end, transmission, control, display and recording. The front end part includes one or more cameras and their supporting lenses, PTZ, protective cover, decoding driver, etc; The transmission part includes cables and / or optical cables, as well as possible wired / wireless signal modulation and demodulation equipment; The control part mainly includes video switcher, PTZ lens controller, operation keyboard, type control communication interface, power supply, supporting console, monitor cabinet, etc; Display and recording equipment mainly includes monitor (display), hard disk video recorder, multi picture splitter (splicing TV wall), etc.

(1) Front end camera

The front-end camera part includes camera, lens, protective cover, PTZ and decoder. The camera part is not only the front end of the whole monitoring system, but also the eye of the whole system. Its function is to change the optical signal of the monitored target into electrical signal. The camera is installed on a monitoring point, and the field angle covers the whole monitored area. If the monitoring area is large, a zoom lens can be installed on the camera to make the camera observe farther and more clearly; The camera can also be installed on the electric PTZ. Through the control of the console, the PTZ can drive the camera to rotate horizontally and vertically, so as to maximize the angle and area covered by the camera.

Since the camera part is the front end of the whole monitoring system, and the situation of the monitoring site is that it transmits the monitored content programming image signal to the monitor in the control center, the camera part is the original signal source of the system. Therefore, the quality of the imaging part and its generated image signal affects the quality of the whole system, and it is also the biggest factor affecting the system noise, so it is very important to select and process the imaging part.

(2) Transmission part
The transmission part is the signal path of the system. The transmitted signals include image signals and signals that the control center controls front-end devices such as cameras through the console. The main transmission content is the image signal. After the image signal passes through the transmission system, it is required not to produce obvious noise and distortion of chroma signal and brightness signal, so as to ensure that the definition and gray level of the original image signal do not decrease significantly. This requires the transmission system to have good performance in attenuation, noise introduction, amplitude frequency characteristics and phase frequency characteristics.

The determination of transmission mode in TV monitoring system mainly depends on the distance of transmission and the number of cameras. When the transmission distance is close, the video baseband transmission mode is adopted; When the transmission distance is long, RF wired transmission mode or optical fiber transmission mode shall be adopted.

(3) Control part: mainly matrix and its keyboard, which are used for video switching function and communication control of camera action with PTZ.

(4) Display and recording part: the display part is a monitor and the recording part is a hard disk video recorder.