Anti-theft Alarm System Principle and Intelligent Development Trend

Today's anti-theft alarm technology to enter the homes of ordinary people, then everyone on the anti-theft alarm technology in the end to understand how much? What is its technical principle? Can you prevent thieves? Please read this article!

The development process of anti-theft alarm The modern anti-theft intrusion alarm technology is constantly developed and perfected in the process of fighting against criminals. Early theft or sabotage, the general use of break through the window to enter the crime site for theft, destruction of crime, for this type of theft damage, researchers developed a switch-type anti-theft alarm detector, this alarm device is simple structure, easy installation and use, Can be installed in the doors, windows, safes and drawers or under the valuables, etc., when the criminals open the doors and windows, drawers or take away valuables, it will cause the switch state to change, trigger the alarm to generate an alarm.

However, as time went by, some criminals learned about the diagnosis and treatment of the switch alarms. Therefore, they did not enter the doors and windows when committing crimes. Instead, they dug walls and made holes to enter the room. In order to effectively deal with such crimes, people developed glass. Break alarms and vibration alarms, when criminals try to break the window glass or dig holes into the wall, they will cause glass break alarms or vibration alarms to generate alarms. Later, people discovered that some thieves used certain places (such as museums, shops, etc.) to open up to people during the day, used some hidden corners in these places during the day, closed the doors at night, and then came out to commit crimes. Two days after the door opened, he sneaked away.

In order to deal with such thieves, researchers have developed a space movement alarm (ultrasonic alarm, microwave alarm, passive infrared alarm, video alarm, etc.), the characteristics of space movement alarm is: as long as the alert space is active Will trigger an alarm. The successful development of space mobile alarms is a major advancement in burglar alarm technology. Early space movement alarms were single-technology alarms. Their biggest drawback was that they were susceptible to environmental noise and led to false alarms, in order to overcome single-technology alarms. The disadvantage of a high false alarm rate was that Japan first proposed the idea of ​​a dual-technology alarm in 1973, but the actual development of a practical dual-technology alarm was in the 1980s. Dual-technology alarms combine two different detection technologies. When both sense the target, they will send an alarm signal. If only one of the detection technologies detects the target, it will not alarm. Dual-technology alarms use two different detection technologies to detect the prevention sites at the same time. It exerts the advantages of different detection technologies, overcomes each other's shortcomings, and greatly reduces the false alarm rate of dual-technology alarms. improve.

At present, the most widely used microwave/passive infrared dual technology alarms. One of the biggest achievements in the field of alarms in recent years is the successful development of digital video alarms. Digital video alarms are a new type of alarm that emerged with the development of digital circuit technology, computer technology and television technology. With the alarm technology in one, with monitoring, alarm, review and image recording forensics multiple functions, is currently the most advanced alarm.

Early burglar alarms were mainly used indoors. With the continuous development and improvement of alarm technology, people have now developed a variety of alarm devices that can be used outdoors to prevent the perimeter. Such as active infrared alarm, laser alarm, microwave wall alarm, electric field sensor alarm, electret cable alarm, leak cable reporter and so on. They have their own characteristics, are suitable for use under different environmental conditions, and have an alarm detection effect on the perimeter of the prevention site.

Composition of anti-theft alarm system A complete anti-theft alarm system usually consists of three parts: intrusion detector, transmission system and alarm controller.

The intruder detector is a front-end device of the alarm system and is installed in a place of demand prevention. The intruder is discovered by detecting changes in the status of the site or some physical parameter, and an alarm trigger electrical signal is sent to the alarm controller through the transmission system.

The intrusion detector is a key part of the entire alarm system. It largely determines the performance indicators of the alarm system, such as detection range, detection sensitivity, false alarm rate, and false negative rate. There are many types of intruder detectors and their functions vary. According to the size of the detection range, the intrusion detector is a bit, line, surface, space and perimeter control type; according to the detection diagnosis of the intrusion detector, the intrusion detector has various types such as switch, vibration, microwave, ultrasonic, infrared and so on. A large-scale anti-theft alarm system generally requires multiple intrusion detectors. The use of different types of detectors in conjunction with each other can make the alarm system more complete, reliable, and more effective.

The detector is used as a sensor detection device to detect the intruder's intrusion behavior and various abnormal conditions. There are many places where security precautions are required in various smart buildings and ordinary buildings. These sites also have various safety precautions and requirements depending on the actual situation. Therefore, a variety of alarm detectors are required to meet different security requirements.

According to the actual site environment and the user's security requirements, a reasonable choice and installation of various alarm detectors can better achieve the purpose of security. When choosing and installing an alarm detector is not appropriate, there may be loopholes in security precautions, failing to meet the strictness of security precautions and creating an opportunity for intruders, thereby bringing undue losses to the security protection work.

Alarm detectors require tamper-proof and vandal-proof functions. When the alarm detector is damaged, people short-circuit or open circuit their transmission lines, and they illegally attempt to open their protective covers, they should all be able to generate alarm signals; in addition, the alarm detectors should also have certain anti-jamming measures to prevent all kinds of errors. The phenomenon of newspapers, such as: prevention of pets and pet harassment, resistance to false positives due to changes in environmental conditions, etc.

The sensitivity and reliability of the alarm detectors influence each other. Reasonably selecting the detection sensitivity of the alarm detector and adopting different measures against external interference can improve the performance of the alarm detector. The use of different anti-jamming measures determines the performance of the alarm detector in different environments. Understand the performance and characteristics of various alarm detectors. According to different use environments, rational allocation of different alarm detectors is the key link of an anti-theft alarm system.

The alarm transmission system refers to the electronic device and signal transmission channel that play the role of alarm signal transmission. The intrusion detector finds that the alarm triggered by the intrusion triggers an electrical signal to be transmitted from the transmission system to the alarm controller; and the alarm controller needs various control signals (such as the arming and disarming of the detector) and the detector The power supply is also transmitted from the alarm controller to the detector by the transmission system. The transmission mode of the alarm signal can be divided into two types of wired transmission and wireless transmission. In the wired transmission, it also includes dedicated line transmission, telephone line transmission, power line transmission and so on.

The alarm controller is the core device of the entire alarm system. Its role is to receive the alarm triggering electrical signal output by the intrusion detector, display the alarm status, sound, light alarm and indicate the location of the invasion and function control of the intrusion detector ( Such as arming, disarming, etc.).

The alarm controller is installed in the duty room. The alarm controller is usually in direct contact with the on-duty personnel. Because the alarm controller is the core device of the alarm system, people are customarily called the host of alarm equipment. There are many types of alarm controllers, but there is no clear classification standard. The simple alarm controller can only control several detectors and has fewer functions. The complex alarm controller can control dozens or even hundreds of detectors and has perfect functions.

Current advanced alarm controllers can display alarm status, alarm location, alarm time, etc. in the form of sound, light, digital, or image. When recording is required, they can be automatically printed, recorded, recorded, or memorized. The advanced alarm controller also has several other functions and vandal-proof functions, such as self-checking of the system's normal state, fault alarm, password switcher, remote control operation, breakage of the transmission line, short circuit alarm, power supply undervoltage alarm, intrusion detector enclosure Demolition of alarms, etc.

Trends in the development of anti-theft alarm technology At present, the detection methods of the detectors used in the security alarm system are mainly to detect changes in the physical quantity and status of the environment. This detection method does not inherently have the ability to identify the detection target of video surveillance. . Therefore, the security alarm monitoring system will be triggered due to some unexpected conditions or affected by environmental factors, resulting in false alarms. For this reason, the intrusion detectors of the security alarm system employ multiple detection elements, multi-technical composite detection, and intelligent data analysis methods, which have greatly improved the performance and functionality of the detectors, and have also reduced Alarming, but this does not fundamentally solve the problem. Therefore, for high risk levels and protection levels, the security alarm system must use a variety of different detection technologies to form intrusion detection systems to overcome or reduce false alarms due to certain unexpected conditions or environmental factors. An audio and video review device is installed, and when the system alarms, an audio and video review device is started to perform audio and video review of the alarm zone.

The intelligentization of the security system can be understood as: realizing real detection, realizing the automatic recognition of image information and various features (various defined features, different carriers, and biometrics), accurate and effective system linkage mechanism and related systems , public - tune the interaction. Intelligence is the development trend and major topic of detection technology. The realization of real detection is always the goal pursued by the detection technology and the direction of research. Due to the limitations of diagnostics and management, the detectors usually have very poor authenticity, coupled with the existence of multiple interference factors, and the false alarm rate of the detection system Hey - very high. At that time, the solution to this problem was mainly the use of alarm evaluation techniques, such as the use of television to observe the scene of the alarm, to determine whether it is a real alarm. At the same time, people are trying hard to improve the authenticity of detection in many aspects. This is the development of intelligent alarms. These studies have achieved certain results, and to some extent have improved the problem of high false alarm rates. The main products that have been rampant-productized and applied are:

Improvements in the structure of the detector element: typically the detector element structure of a passive infrared detector. The multi-element infrared detector uses the difference of the geometrical position of different elements and the optical modulation of the optical system (Fresnel lens group) to generate the interference suppression effect. Take bi-ary as an example: due to the difference in the geometric positions of the two elements, when they receive thermal radiation energy from the same (moving) target, there will be a difference in the degree of radiation (the size of the received energy) and the phase difference. (in chronological order). Differentiating the output of two yuans can improve the detection sensitivity. At the same time, because the interference of the environmental factors (mainly the change of the background temperature) is the same for both elements, there is no differential output, which also plays a role in suppression. Currently, the market's high-end passive infrared detectors have dual (two detectors), four yuan (four detectors), and dual S (four irregular detectors), which are the main choices for high security requirements. . Due to the limitation of manufacturing technology, the products mainly come from foreign countries and the prices are relatively high.

The combination of detection technologies: It is an effective method to combine two different diagnostic-physiological detection technologies to complement each other in performance. This is the so-called Shuangjian detector. Its appearance is an important stage in the development of detection technology. It is the beginning of the intelligentization of detectors and has become the mainstream product of high-end intrusion detectors. Microwave/PIR is the most widely used dual technology detector. At present, there is a saying on the market that it uses the intelligent processing of detector signals as a guide. It is not a combination of three detection technologies. It is still a Shuangjian detector.

Intelligent detectors: Due to advances in microprocessors and DSP technology, many electronic devices are equipped with CPM units for intelligent signal processing. The main forms of intelligent detectors are: detection signal processing is no longer simple. Set a threshold value, that is, when the detection signal exceeds, an alarm is generated, and pulse counting (PIR), time delay (active infrared, microwave, etc.) and other methods are used to determine whether the detection is an accidental event (single or instantaneous ); detector adaptive design, its alarm threshold can be adjusted adaptively with changes in environmental factors, it improves the detection of environmental adaptability and the ability to suppress interference; intelligent detection of the detection signal, energy analysis or frequency Analysis is the two main methods.

The new detection principle and detection technology research: At present, the detection equipment applied in the security system is mainly to detect changes in the physical quantity and state of the environment. This detection method does not inherently have the ability to identify the detection target. Therefore, the accompanying false alarm problem has been plaguing the security system. The use of multiple detector elements, multi-technical composite detection, and intelligent data analysis has indeed greatly improved the performance and functionality of the detectors and reduced false alarms, but it has not fundamentally solved the problem.

The detection based on target analysis is a technology that directly identifies the target. It is based on image technology or feature recognition technology and is an effective detection method. We know that observing an image on a monitor is the most basic and original detection method. If we can perform dynamic analysis on the image to realize motion recognition, target recognition (automatic recognition), and multi-dimensional detection, video technology will be real The space exploration method is a detection method that does not require review or integration with review.

At present, a variety of video detection devices have been applied, such as the motion detection function of most digital video recording devices, and various image content analysis software have realized the intrusion detection function. It can be foreseen that video technology will change the appearance of detection equipment from principle and form, and it is the main direction of intelligent alarm, which should arouse our attention.