I. Overview of Security System
The often-mentioned safety and security system has three defenses: "human defense, physical defense, and technical defense." Its main definition is as follows:
Air defense: It is the basis of security. The traditional "human defense" refers to the display of human's natural ability in the work of safety precautions. That is, human body senses are used to detect and react, and the occurrence of risk events is postponed and prevented through the exertion of human physical capabilities. Modern "personal defense" refers to an organized preventive action of personnel and/or groups of people with appropriate qualities to perform security prevention tasks, including the training of highly qualified personnel, the deployment of advanced self-defense devices, and the organization and management of personnel. Wait.
Physical defense: Various physical protection measures (including structures, barriers, appliances, equipment, systems, etc.) that can be used for security purposes and that can delay the occurrence of risk events.
Technical defense: The use of a variety of electronic information equipment to form a system and / or network to improve the detection, delay, response capabilities and protection features of security measures.
Second, the perimeter to prevent the purpose
The main achievement is that when someone climbs and crosses a predetermined defense zone, they can reliably alarm when intruding, and they can link the video surveillance system to accurately locate the alarm zone. When no one climbs, even when the wind, rain, snow, lightning and other bad weather The alarm system does not generate false alarms when the vehicle is passing through and the animals are present.
According to the functions of the main subsystems of the 3.3.3 security protection system of the "Safety and Preventive Engineering Technical Specification GB 50348-2004", the important entry of the intrusion alarm subsystem: the system shall have no leakage alarm, and the false alarm rate shall meet the requirements of the engineering contract.
Third, perimeter protection system technology classification
According to source classification
In accordance with changes in the electromagnetic environment detection: tension network, hydraulic buried detection, vibration cable, vibration cable.
According to electromagnetic environment change detection: microwave radiation, underground leakage cable, electrostatic induction cable, high-voltage pulse network (electronic fence)
According to the light intensity change detection: infrared radiation, laser radiation
In the form of a detector
Tangible: tension net, vibration cable, vibration cable, static induction cable, high voltage pulse grid (electronic fence).
Invisible: infrared radiation, laser radiation, microwave radiation, buried leakage cable, hydraulic buried detection
IV. Introduction of various detection technologies
Infrared radiation:
Infrared shot full name is "Active Infrared Intrusion Detector. Its basic structure includes transmitting end, receiving end, beam intensity indicator, optical lens, etc. Its detection principle is to use the LED infrared emitting diode to launch. The pulsed infrared light is then focused by an optical mirror to allow the light to travel a long distance and is received by the receiver, and an alarm is issued when the infrared pulsed beam is interrupted.
Advantages: Is there? .......Cheap.
Disadvantages: My God! Factors such as birds, animals, temperature, light, air flow, fog, rain and snow, as well as installation methods, angles, locations, etc., can easily lead to false alarms. So according to my experience this technology should be applied indoors! Outside the installation, several users have all the power off, otherwise all day mistakenly alarm security personnel will be crazy, or aunt!
Laser shot:
Laser intrusion detectors are active intrusion detectors and consist of a laser transmitter and a laser receiver. The laser transmitter consists of a laser transmitter, a modulated excitation power supply, and a corresponding direction adjustment device; the laser receiver consists of a laser receiver, an optoelectronic signal processor, and a corresponding support mechanism.
Advantages: Low price, no impact on light compared to infrared.
Disadvantages: Fly birds, animals, temperature, air flow, fog, rain and snow, etc. Environmental factors as well as installation methods, angles, and location are all very likely to cause false positives. Several have the same disadvantages as infrared technology, false alarm rates, and relatively less infrared technology. There are no trees around the general community project and they are recommended for use. Other projects are not recommended for use, especially for projects with higher levels of prevention.
electric fence
The output terminal of the electronic fence generates a high-voltage pulse and transmits it to the front fence. The front-end fence that forms the loop sends the pulse back to the host receiver. If someone passes (short-circuits), cuts (breaks) the front fence or destroys the host, the host will generate an alarm. Signals, and the alarm signal at the same time passed to the scene of the alarm and monitoring center.
Advantages: 1. Set "deterrence, blocking, alarm, security" in one.
2. Low false alarm rate, strong anti-interference ability, accurate alarm, overcoming technical defects such as infrared, microwave, and electrostatic induction.
3. The perimeter electronic fence can be erected with the relief of the terrain. The gates and corners can be installed.
Disadvantages: When the intruder crosses the guardrail across the clothes or gloves, there is no alarm reaction, and then there are no alarms when the criminals use a soft sheathed cable to short-circuit the fence around or up and down, and then cut off the original electronic fence. Reaction, which greatly jeopardized the security of the area.
Microwave shot
The microwave detector consists of a transmitter and a receiver. After the system is started, an invisible spindle-type stereo detection area is formed between the transmitter and the receiver. The size of the detection area depends on three factors: the type of antenna used, the distance between the transmitter and the receiver, and the sensitivity set by the receiver. The size of the zone is 10m-120m.
There are two types of microwave-based microwave detectors for analog microwave and digital microwaves. Analog microwaves can only determine whether the signal attenuation reaches a set value. Digital microwaves can analyze and adjust signals, such as weight and speed. Generally 20-40 kg, 0-15 meters per second can be set.
Advantages: Microwave working frequency is 10GHZ, away from the spectrum, unaffected by adverse weather conditions, the human eye is completely invisible, intangible, confidentiality is good, can not be overturned, the installation is simple, can be installed on the wall, fence, can also be landing Independent installation. The false alarm rate is low.
Disadvantages: 1. The zone is a straight line and there must be no more than 20 kilograms of moving objects in the zone.
2. Interfered by radar, does not apply to units using radar.
3. The distance between the transmitter and the receiver affects the detection rate. It is recommended not to exceed 80 meters in one zone.
Leakage cable
The leaky coaxial cable is used as a sensor and consists of two leaky cables buried in the perimeter of the perimeter, a transmitter and a receiver. Leakage cable is a coaxial cable with a special structure that periodically opens certain shaped slots in the longitudinal direction of the outer conductor of a common coaxial cable. The space between the two leaking cables forms a detection area of ​​an elliptical electromagnetic field. When someone enters this detection zone, it will interfere with the electromagnetic coupling of the detection zone, and the energy of the electromagnetic wave received by the receiving cable will change, and thus an alarm signal will be generated.
Advantages: 1. Is a kind of concealed perimeter defense system, generally underground or into the wall, does not affect the appearance of the scene, but also belongs to the intangible detection field, the intruder can not detect the existence of the detection system, can not avoid or destroy the system .
2. The cable can surround the perimeter of the alert area of ​​any shape and is not limited by factors such as terrain and unevenness of the ground.
3. The detection sensitivity of the system is not affected by the climate, environment, temperature, weather, smoke and dust. Can work reliably in all weather.
Disadvantages: 1. Leakage cable is not suitable for a wide range of applications, about 100m in length
2. Need power supply, large power consumption
3. Soil moisture will also affect the accuracy of the alarm. It will cause false alarms due to water or metal movement in the area..
Tension fence
The tension fence system is designed to be mechanically inductive. The perimeter is made up of wire and column nets that are tensioned in parallel with a certain tension. It is generally a zone every 60 meters. Vertical acquisition signal is installed on the middle detector column of each zone. Wire and connect with the detector. The detector is connected to the system's control center using signal wires. When there is an invasion, its force causes the current balance to be destroyed and perceived by the detector. Climbing, cutting off, pulling up, and damage to equipment can trigger an alarm and notify the system control center via the detector. The tension fence system has the characteristics of self-balancing and continuous fortification. After the perimeter is tightened and the wire is destroyed, the system can still alarm the next damage in the new self-balancing state before the system is repaired. This feature can prevent the entire system from being paralyzed due to the failure of the wire to be repaired at night due to wire breakage.
Vibrating cable
The perimeter of the vibrating cable is composed of controllers and cables. The controller can connect 1-2 lines. The principle is that there are two sensing cables near the circumference of the center conductor. The induction cable is suspended in a solid keyway made of polyethylene. The physical deformation of the cable causes the sensing cable to produce movement relative to the center coaxial cable and the external cable. Motion will be detected and accurately positioned. The size of the zone is 10m-400m.
Advantages: Long detection distance, unaffected terrain, accurate positioning, simple installation, can be installed on the wire mesh at the top of the wall, or installed on the fence
Disadvantages: There must be a vibrating body attached, bad weather or birds can cause false positives. Can be overturned.
Vibration fiber
Vibration fiber, commonly known as "optical fiber fence", there are two kinds of zone type, positioning type, the installation method is linked to the net or buried two. The principle is to use optical fiber that is sensitive to external vibration and pressure and has sensing function as a sensing medium, integrates “transmission†and “feelingâ€, and senses the role of optical fiber in external physical factors (such as movement, vibration, and pressure). Next, change the transmission parameters (phase, wavelength, power, etc.) of the light in the fiber to detect and alarm the external vibration and pressure.
V. Comparison of various detection technologies
Any perimeter warning technology is not without its drawbacks. It is necessary to make the most appropriate plan according to specific projects and specific circumstances. At the same time, a perfect security system is by no means a technical precaution that can be solved, or that sentence: technical defense, Physical protection, air defense.
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