With the continuous rapid development of China's economy, the security technology market has been fully developed. A variety of technologies used in security technology facilities, to maintain public security, to protect people's lives and property security has played an important role. Among them, the most widely used and developed for a long time is the video surveillance system. In this paper, we mainly take the video surveillance system of intelligent building as an example to explain the working principle of PoE switch in this video surveillance system, as well as the general design method and the problems that need attention.

Intelligent Building Monitoring System Design
Intelligent building video surveillance system design points: according to the builder on the system function requirements and investment, to determine the technical indicators of the system and equipment composition, including network video surveillance system, network transmission system, transmission cables, storage devices, display devices and other systems; according to the system composition, to determine the equipment configuration, according to the building plane characteristics, to determine the installation location of cameras and other equipment; in accordance with the monitoring objectives and Surrounding environmental conditions, select the type of camera and protective measures; according to the camera distribution and environmental characteristics, to determine the transmission line laying; and finally consider the video surveillance system and intelligent building "3AS" (building automation system, communication automation system, office automation system) docking.
In the building security system, the video surveillance system enables managers in the control room to observe the situation at all important locations in the building, providing a visual effect for the security system; in the visual intercom system, each household can access the host through the home user terminal and the door for visual intercom, remote locking and other tasks. Create a secure communication bridge between visitors and users.
The intelligent building network video surveillance system designed by this solution can be divided into subsystems such as the front-end image acquisition system, PoE power supply and network transmission system, display and recording system, and centralized management system according to their functions.

Front-end: install millions of HD PoE network cameras at each monitoring point, and choose different models such as ordinary guns, infrared guns, infrared dome and high-speed dome according to different monitoring environments. Install user extensions in every home and doorways in every building.

Transmission: All floors cameras and user extensions are connected with PoE switch through network cable, get power directly from the switch. Enter the weak well floor switch, and then through the network cable all access to the monitoring center room switch.
Monitoring center: The monitoring center mainly consists of four parts, the core switch, NVR host, TV wall and management host. All the front-end camera signals are connected to the PoE switch converge, and then access the core switch room, each NVR host also access the core switch, each host displays 32-channel images, video data stored in each NVR host, according to the recording time need to mount different sizes of hard disk or disk cabinets.
Sub-control center: including sub-control center management host, display equipment.

Elevator Monitoring

Elevator monitoring is a very important part of intelligent building network video monitoring, because the elevator shaft is a more complex environment, many projects in the elevator monitoring by different degrees of interference, at present, most of the elevator transmission is to use video baseband (twisted pair) transmission or increase the anti ***** transmission, of course, can also use radio frequency transmission or wireless transmission solutions.
The following is a simple system diagram of PoE elevator transmission solution for reference.

PoE Elevator Solutions
Of course, the simplest and most convenient way is to use a pair of wireless bridges to transmit the elevator camera video images to the monitoring center.

Advantages and features of PoE switch in this solution

Low difficulty and low cost for construction and maintenance: there is no need to lay a large number of video cables, power lines and use specific transmission equipment, the system adopts the bus distributed networking mode, simple construction, low cost for the required transmission equipment, and conducive to future maintenance.
Flexible and secure: PoE requires only one twisted pair cable, which is simple and space-saving, and the device can be moved around. Moreover, PoE powered devices only supply power to the device that needs it. Only when the device is connected to the Ethernet cable will voltage be present, thus eliminating the risk of leakage on the line.

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