What are the common perimeter defense alarm systems? Do you know?
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November 19 15:03:45, 2024
Speaking of the perimeter defense system, the first thing you may think of is the infrared alarm system, followed by the electronic fence system. In fact, the application of the infrared alarm system in the perimeter prevention is gradually reduced. The electronic fence system gradually replaces the perimeter infrared alarm system. What are the subsystems of the two systems, the perimeter defense system? Today, we will focus on some of the common systems in the perimeter defense system.
First, the security system overview
It is often said that the security system has three defenses: "human defense, physical defense, technical defense". Its main definitions are as follows:
Civil air defense: it is the basis of security. The traditional "human defense" refers to the display of people's natural ability in security work. That is to use the human senses to detect and react, and to delay and stop the occurrence of risk events through the physical exertion of the human body. Modern "personal defense" refers to an organized preventive behavior of personnel and/or groups of people of appropriate quality who perform safety precautions, including the cultivation of highly qualified personnel, the configuration of advanced self-defense equipment, and the organization and management of personnel. Wait.
Physical defense: Various physical protection means (including buildings, structures, barriers, appliances, equipment, systems, etc.) that can be used for safety prevention purposes and can delay the occurrence of risk events.
Technical defense: A system and/or network that uses various electronic information devices to improve the security, detection, delay, response and protection functions.
Second, the perimeter prevention purposes
It mainly realizes that when someone climbs and traverses a predetermined defense zone, it can reliably alarm when invading, and can link the video surveillance system to accurately locate the alarm zone, while no one climbs, even in bad weather such as wind, rain, snow, lightning, etc. The alarm system does not generate false alarms when the vehicle passes through and the small animals.
According to the "Safety Protection Engineering Technical Specification GB 50348-2004" 3.3.3 The functions of the main subsystems of the security system, the important items of the intrusion alarm subsystem: the system must not have a leak alarm, and the false alarm rate should meet the requirements of the engineering contract.
Third, the perimeter of the defense system technical classification
Classified by source
According to changes in electromagnetic environment: tension net, hydraulic buried detection, vibration cable, vibrating cable.
Detection of changes in electromagnetic environment: microwave radiation, buried leakage cable, electrostatic induction cable, high voltage pulse grid (electronic fence)
Detection according to weak light intensity: infrared radiation, laser radiation
Follow the detector form
Tangible: tension mesh, vibration cable, vibrating cable, static induction cable, high voltage pulse grid (electronic fence).
Invisible: infrared beam, laser beam, microwave beam, buried leak cable, hydraulic buried detection
Fourth, various detection technology introduction
Infrared radiation:
The full name of infrared radiation is called “active infrared intrusion detector. Its basic structure includes transmitting end, receiving end, beam intensity indicator, optical lens, etc. The detection principle is based on the emission of LED infrared light emitting diode. The pulsed infrared light is then focused by the optical mirror to transmit the light to a long distance and is accepted by the light receiver. When the infrared pulse beam is interrupted, an alarm is issued.
Advantages: Is there? ....... cheap.
Disadvantages: My God! Environmental factors such as birds, animals, temperature, light, air flow, fog, rain and snow, as well as installation methods, angles, locations, etc. are all prone to false positives. So according to my experience, this technology should be applied indoors completely! Installed outdoors, a few users are all out of power, otherwise the security guards will be mad all day, or 骂 mother!
Laser beam:
The laser intrusion detector belongs to the active intrusion detector class and consists of a laser transmitter and a laser receiver. The laser transmitter is composed of a laser transmitter, a modulated excitation power supply and a corresponding direction adjusting device; the laser receiver is composed of a laser receiver, a photoelectric signal processor and a corresponding supporting mechanism.
Advantages: low price, compared to infrared radiation is not affected by light.
Disadvantages: factors such as birds, animals, temperature, air flow, fog, rain and snow, as well as installation methods, angles, locations and other factors are prone to false positives. Several of the shortcomings of the infrared technology are the same, the false alarm rate and the relative infrared technology are less. There are no trees around the general community project, it is recommended to use, other projects are not recommended, especially for projects with higher levels of prevention.
electric fence
The output of the electronic fence main unit generates a high-voltage pulse and transmits it to the front-end fence. The front-end fence forming the loop transmits the pulse back to the receiving end of the host. If someone crosses (short-circuit), cuts (breaks) the front-end fence or destroys the host, the host will generate an alarm. Signal and transmit the alarm signal to the alarm and monitoring center at the same time.
Advantages: 1. Set "deterrent, blocking, alarm, security" in one.
2. The false alarm rate is low, the anti-interference ability is strong, the alarm is accurate, and the technical defects such as infrared, microwave and electrostatic induction are overcome.
3. The perimeter electronic fence can be erected with the terrain, and the gates and corners can be installed.
Disadvantages: When the intruder crosses the guardrail across the clothes or gloves, there is no alarm response. Then the criminals use the soft sheath line to short the fence to the left or the right or the upper and lower, then cut the original electronic fence and go over without warning. The reaction, which greatly jeopardized the safety of the zone.
Microwave radiation
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 the type of antenna used, the distance between the transmitter and receiver, and the sensitivity of the receiver setting. The size of the zone is 10m-120m.
Microwave detectors are divided into two types of analog microwave and digital microwaves. The analog microwave can only determine whether the signal attenuation is reached. The digital microwave can analyze and adjust the signal, such as weight and speed. Generally 20-40 kg, 0-15 meters per second can be set.
Advantages: The microwave working frequency is 10 GHz, away from the spectrum, and it is not affected under bad weather conditions. The human eye is completely invisible, intangible, and has good confidentiality. It cannot be overturned. It is easy to install and can be installed on the wall, on the fence, or on the ground. Standalone installation. The false alarm rate is low.
Disadvantages: 1. The zone is a straight line, and there must be no moving objects larger than 20 kg in the zone.
2. Subject to radar interference, not applicable 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 for a zone.
Leaky cable
The leaked coaxial cable is used as a sensor, consisting of two leaky cables buried in the perimeter and a transmitter and receiver. The leaky cable is a coaxial cable having a special structure in which a slot having a certain shape is periodically formed in the longitudinal direction on the outer conductor of the ordinary coaxial cable. The space between the two leaking cables forms an area of ​​detection of an elliptical electromagnetic field. When someone enters the detection zone, it will interfere with the electromagnetic coupling of the detection zone, and the electromagnetic wave energy received by the receiving cable will change, thereby generating an alarm signal.
Advantages: 1. It is a concealed perimeter defense system. It is generally underground or installed in a wall. It does not affect the appearance of the site. It is also an invisible detection field. The intruder cannot detect the existence of the detection system and cannot avoid or destroy the system. .
2. The cable can surround the perimeter of any shape of the warning zone, and is not limited by terrain, uneven ground and other factors.
3. The detection sensitivity of the system is not affected by the climatic environment such as ambient temperature, temperature, wind and rain. Work reliably 24/7.
Disadvantages: 1. Leaky cable is not suitable for a wide range of applications, length is about 100m
2. Power supply, high power consumption
3. Soil moisture will also affect the accuracy of the alarm. It will cause false positives due to the water or metal movement of the ground area..
Tension fence
The tension fence system is designed to be mechanically inductive. The perimeter is composed of a wire and a column net that are tensioned in parallel by a certain tension. Generally, it is a zone every 60 meters. Vertically collected signal iron is installed on the middle detector column of each zone. Wire and connect to the detector. The detector is connected to the control center of the system with signal wires. When there is an intrusion, its force causes the balance that is now maintained to be destroyed and perceived by the detector. Climbing, cutting, 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 arming. After the perimeter tensioning wire is destroyed, the system can still alarm the next damage under the new self-balancing state before the repair. This feature prevents the entire system from being paralyzed by night wire damage due to wire damage.
Vibration cable
The perimeter of the vibrating cable consists of a controller and a cable. The controller can be connected to the 1-2 line. The principle is that there are two sensing cables near the circumference of the center conductor. The sensing cable is suspended in a solid keyway made of polyethylene. The physical deformation of the cable causes the sensing cable to move relative to the central coaxial cable and the external cable, and the motion will be detected and accurately positioned. The size of the zone is 10m-400m.
Advantages: long detection distance, unaffected terrain, precise positioning, simple installation, can be installed on the top of the wall, or installed on the fence
Disadvantages: There must be attached vibrations, bad weather or birds can cause false positives. Can be overridden.
Vibration fiber
Vibrating fiber, commonly known as "fiber fence", has two types of anti-zone type and positioning type. The installation method is either hanging net or buried. The principle is to use the fiber that is sensitive to external vibration and pressure and has sensing function as the sensing medium, which combines “transmission†and “sensingâ€, and the role of sensing fiber in external physical factors (such as motion, vibration and pressure). Next, change the transmission parameters (phase, wavelength, power, etc.) of the light in the fiber to detect and alarm external vibration and pressure.
V. Comparison of various detection technologies
Any perimeter alarm technology is not without its shortcomings. It is necessary to make the most suitable solution according to the specific project and specific environment. At the same time, a perfect security system is by no means a technical defense can be solved, or that sentence: technical defense, Physical defense, civil defense.