The principle and development history of electronic fence

First, the development process of electronic fences:

1. What is an electronic fence? An electronic fence is an intelligent perimeter system consisting of a pulse generator (host) and a front fence. The modern public safety electronic fence has evolved and improved to become a new type of perimeter alarm product. It has changed the traditional model of simple post-warning in the former perimeter protection and emphasized the use of blocking (visible fences, manufacturing of intrusion barriers) as The main and alarm (acousto-optical alarms can be linked with Other security systems) are supplemented by the new concept of international perimeter security with the role of deterrence (reducing the desire to commit crimes), while the product overcomes the shortcomings of the AC grid that are fatal and affect aesthetics, and the traditional Compared with perimeter security systems such as infrared, microwave, and electrostatic induction, it has the advantages of low false alarm rate, free from terrain and environmental constraints, and high safety. It has been widely used in substations, factories, communities, schools, villas, warehouses, and airports. , military bases, detention centers, prisons and other places.

2. The Evolution of Electronic Fences After a long period of development, electronic fences have gone through three stages:

(1) The first stage: The electronic fence first originated from the mobile grazing land in Europe. The shepherd pulled a wire and connected it with DC power for the purpose of grazing. A simple electronic fence was formed to enable the animals to move within a certain range. After the war, in Europe, the proportion of animal husbandry in agriculture was very high, and a large number of animal husbandry market demands promoted the development and promotion of “electronic fences”. Cattle and sheep encountered the electric fence of the “electronic fence” and returned it, playing a good role as a “shepherd”. At the same time, they also prevented large animals or beasts running outside the circle from entering. This played a major role in the development of the animal husbandry at the time. The promotion is still playing a bigger role in some countries with relatively developed animal husbandry.

(2) The second stage: With the development and deepening of the entire "electronic fence" industry, more and more product accessories and types, intelligent perimeter security alarm system with blocking and alarm functions in the middle and late 90s, began professional use In the field of social public safety, it has the functions of open circuit, short circuit and power failure alarm, and it also upholds the safety barrier function of electronic fences. The product fully considers the initiative and wisdom of people, can accurately determine the unintentional touch, intentional destruction, illegal intrusion and other conditions, is a relatively good choice for the current perimeter security project.

(3) The third stage: As people's demands for product performance and functions become higher and higher, products need to be more humane, and products with more functions begin to appear. The second stage of the product output pulse voltage is constant, so that when the perimeter changes, the voltage at the front end will appear too high or too low with the length of the perimeter; at the same time when the product is installed in a villa with a lower wall or In the community, accidental hitting of children or nearby staff occurs during the day. Based on the above problems, there are now more advanced products that can adjust the output voltage and can set the high voltage mode, safe mode switching function. When switching to the safe mode, the hand touches the electronic cable without electric shock feeling, but if it is destroyed, still An alarm signal will be issued. At the same time, the products at this stage also have remote control, remote operation, and other functions, providing better products for large-scale applications in villas and communities.

Second, the electronic fence alarm principle 1, the working principle of electronic fence pulse generator (host) power after the launch port to the front fence issued a pulse voltage, the time interval of about 1.5 seconds to launch 1 time, the pulse on the fence to stay about 0.1 seconds, After forming a loop on the front fence, the pulse is returned to the receiving port of the host. This port receives the pulse signal fed back; at the same time, the host also detects the resistance value between the two transmitting terminals. If the front end fence is broken due to destruction or short circuit, pulse receiving port does not receive pulse signal or the resistance between the two transmitter terminals is too small, the host will issue an alarm.

2, the fence alarm through the working principle of the electronic fence can know, no matter the pulse host is in what kind of voltage working condition, when the fence is damaged, the receiving port can not receive the pulse signal, the pulse host will alarm; Similarly, when the two electrons Short circuit between the cable, the resistance is very small, the pulse of the host will alarm.

Third, the delimitation of the fence zone currently on the market pulse controller can generally control the number of single-line meters in the 10000 meters, if the market generally installed on the 4-lane fence to calculate the length of the fence is about 2500 meters, so long If an alarm occurs, the security personnel will take a long time to find the location of the accident and cannot handle it in time. At the same time, Shanghai Technical Defense Office also requires that each zone of the perimeter alarm system should not exceed 100 meters. Therefore, it is necessary to divide the defense zones. Through technological transformation or the introduction of new products, there are two ways to divide the defense zone. The first one is where one host controls two defense zones, and one machine has two defense zones. The perimeter of the method controlled by this method is limited in length and is only applicable to relatively short weeks. The sector cannot generally exceed 250 meters. When the perimeter is longer, a large number of mainframes need to be added and the cost is very high. The second method is to use a host to add multiple zone controllers. This can easily divide the long perimeter into multiple zones, reduce costs, facilitate management, and increase security. After dividing the defense zone, you can also use the 485 bus to transmit front-end alarm information through the alarm host. You can use the LED light to display the alarm zone, improve the alarm accuracy of the zone, connect the dialer, and call the alarm center and the 110 network.

Fourth, the design and installation of electronic fence 1, fence design according to different security levels, configure the appropriate to meet the requirements of the electronic fence.

The security level is usually divided into three levels:

(1) Deterrence - One defense zone is set over the perimeter, such as a 4-wire system installed on the top of a wall. With blocking alarm and deterrent effect.

(2) Medium security level. The length of each zone is not more than 300 meters. If it is greater than 300 meters, it should be divided into multiple zones.

(3) Higher security level. The length of each zone is set at 100 meters, and the entire fence is divided into multiple zones. Each zone has its own individual triggering alarm that indicates the zone where the alarm is located. The alarm output is usually linked with other security systems such as CCTV, infrared radiation, spotlights, and alarms. In actual use, the length of each zone should be set according to length, terrain and economic needs.

2. Installation of fences The electronic fences are divided into three types of basic installations: stand-alone, attached and wall-top, depending on the installation location on the site. A free-standing electronic fence is erected directly on the ground. Its height is about 2 meters, and generally 10-12 cables are installed. Considering the safety of equipment and personnel, it is required to install a protective wall or wall of not less than 1.2m on one side or both sides of a self-contained electronic fence. The clearance distance between them should not be less than 1m. Keep the free-standing electronic fence's normal working area in an enclosed area that is generally inaccessible to the public. Attached electronic fences are attached to the wall. Auxiliary electronic fences are mainly used where there is a higher level of safety and do not occupy peripheral land. There are three requirements for the existing fence. First, the wall should have sufficient fastness to withstand the tension and pressure of the electronic fence. Second, the height of the wall should not be less than 2m. Third, the mesh of the wall must be less than 50mm so as not to reach into the hand and touch the electronic fence attached to the inside of the wall. Wall-top type electronic fences are currently more popular in China and are erected on the top or side of the existing wall. Can be installed vertically or at a certain angle. The height of the electronic fence is about 0.8m.