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Perimeter security intrusion systems within the Hong Kong climate

Assessing the capabilities of current perimeter intrusion detection systems in Hong Kong’s home security landscape

HK Backgroud

Being one of the most densely populated regions on the planet, Hong Kong has its fair share of break ins, especially in areas of high wealth concentration. Affluent districts such as The Peak and Repulse Bay see regular incidents of breaking and entering, a phenomenon reinforced by the rising levels of wealth inequality within the city. Studies show that inequality is positively correlated with crime[i], and according to Oxfam’s Hong Kong Inequality Report, Hong Kong has one of the highest worldwide rates of wealth inequality, citing a Gini coefficient of 0.539 in 2016 when analyzing median monthly income.[ii] This is much higher than that of other developed economies such as Singapore (0.356) and the United States (0.391).

In the face of growing discontent among the city’s populace, the question of safety has become increasingly significant, and many of Hong Kong’s institutions are looking at possible additional measures to deter or respond to cases of forced entry. The installation of Perimeter Intrusion Detection Systems (PIDS) in expensive properties and private housing estates are becoming commonplace, but are they enough to ensure the safety of a property and its inhabitants?

Commonly used perimeter intrusion detection systems

Several intrusion detection systems are prevalent both in Hong Kong and around the world. Before making a purchase, clients take into account considerations such as cost, ease of installation, utility, and effectiveness. The most widely used systems are broadly separated into three categories: Video Analytics Systems, Invisible Wave Based Systems, and Physical Contact Based Systems.

Video analytics systems

Video Analytics makes use of simple AI (artificial intelligence) to perform video content analysis when conducting surveillance operations. The AI is capable of advanced functions such as motion detection through cross line detection or zoning, object detection (i.e. differentiating a person from a vehicle), and even facial recognition or license plate recognition. This is accomplished through the use of complex algorithms which set up parameters, or a set of predetermined rules that will trigger a detection response if the conditions are met. These rules may include: the size or shape of the foreign object passing through the camera’s view, the recorded pixel distortion threshold needed to generate a response, or the creation of a digital line or zone which will trigger an alert when breached.


CCTV cameras: Probably the most well-known of all intrusion detection systems, CCTV cameras, or Closed-Circuit Television cameras, is primarily used for its surveillance and recording capabilities, and functions secondarily as a means of detection, identification, and recognition (for more expensive models). Images recorded by CCTV are transmitted by signal to a central hub where they can be monitored or saved for later review.

Consider this scenario: a person walks up to a CCTV camera while entering a property. Walking through a CCTV camera’s pre-programmed zone will cause a distortion in pixels within its field-of-vision and the AI will note this difference, raising a motion detection alert. This alert can be followed by a facial recognition procedure where the camera tries to match the person’s facial characteristics to an internal database record. If these characteristics are unfamiliar, an alarm will be generated. In addition to being wired to an alarm system, modern versions can even send real-time alerts to your phone, allowing for quick and immediate response if there is an emergency.

Strengths: CCTV cameras have advanced significantly over the years. Improvements to pixel resolution, infrared or thermal night time monitoring for greater visual clarity, and automatic pan and tilt have greatly enhanced its surveillance and recording abilities. By making use of video analytics, CCTV cameras can either assist security personnel in identifying possible threats (e.g. highlighting the perceived threat for easy identification), or operate in an individual capacity (activating an alarm if pre-established rules are violated).

Affordable pricing and ease of implementation are also significant factors that have increased CCTV camera use and prevalence. It has become a staple of security in many Asian countries, used by individual home or business owners to secure their properties, and by governments to deter crime and establish stability.

There are currently more than 200 million cameras installed in China alone, with millions more expected by the end of 2020 [ii]

Weaknesses: Despite being an effective and cost-friendly choice for a surveillance system, CCTV cameras aren’t without their drawbacks. Motion detection along with facial and license plate recognition are certainly noteworthy advancements, but they are far from foolproof. For motion detection, parameters can be set so that only objects of a certain size will raise an alert, reducing the risk of false alarms such as passing animals or insects. However, size is proportional to distance. What if a bird were to fly up close to the camera? From the camera’s point of view, the object would certainly exceed the size threshold, and will likely generate an alert. Likewise, facial recognition and license plate recognition are still prone to error. False positive and negative recognitions are common, where the camera misidentifies a ‘friendly’ object to be foreign, and vice-versa. Accuracy may be improved for certain models, but the price is also much higher.  Simply put, these features are not yet at the level to be reliable, fool-proof security measures, and as such, it may be hard to justify spending a premium for them.

Invisible wave based systems

The underlying concept behind these systems is that they receive and detect waves/radiation emanating from objects in its field of view. Invisible Wave Based Systems are normally connected to a main alarm control panel and will send a signal to the control panel if motion is detected, triggering an alarm. Perimeter intrusion detection systems that utilize this include infrared beams, laser scanners, microwave sensors, ultrasonic sensors, magnetic wave sensors, and coaxial cables. Of these devices, infrared is the most common.


Passive infrared sensors: A small, invisible wave based intrusion device that detects and receives infrared light/heat waves. Used widely from government installations to personal properties. Radiation is emitted from sources of heat and invisible to the naked human eye; all objects with a temperature higher than absolute zero emit heat energy in the form of radiation.

Strengths: One of the main benefits of passive infrared sensors is that they are unobtrusive devices that can be hard for intruders to spot if properly concealed or installed in inconspicuous areas. As with all devices that utilize the invisible wave system, they can be calibrated to generate an alert only if the level of radiation passes a certain threshold to prevent responding to motion from birds or small animals. They can also be set to operate at certain hours and in tangent with other security devices such as CCTV cameras or sirens.

Weaknesses: Without support from other security devices, passive infrared sensors alone are incapable of telling apart objects that give off similar levels of infrared heat. In other words, they detect general movement, but do not convey further information such as the person or object that triggered the detection. This makes them susceptible to false alarms because animals give off similar thermal radiation signatures to humans. Calibrating the infrared threshold reduces the chance for this, but similar to the motion detection vulnerability in CCTV cameras, the wavelength of infrared given off also changes with proportion to distance. In other words, a faraway mouse that passes the sensor will probably not trigger an alert, but there is a high chance that a mouse up close to the sensor will. As a result, the utility of passive infrared sensors is maximized when confined to indoor use.

Physical contact systems

These systems are activated only once physical contact has been established with the intrusion device itself. Examples of devices that utilize this system include vibration based sensors, magnetic contact sensors, electric fences, and pressure sensors.


Electric fences: The electric fence is a system that uses an electric shock to deter and prevent intruders from breaching a perimeter. There are three main components to an electric fence: a power energizer or mains, the fence which acts as a conduit, and a grounds rod which feeds back into the energizer. An electrical circuit is completed when the fence is touched, converting power from the power energizer into a short, high voltage pulse.         

Strengths: The main appeal that electric fences offer is the threat of bodily harm to potential trespassers, making it a powerful and effective deterrent. Although signage is required to alert people that the fence is electrified, it may be hard to notice during the nighttime when intrusions are likely to be prevalent, and can prevent an impromptu scaling attempt. Much like other security devices, an electric fence can be integrated with a main alarm system. If a monitoring system is installed, it will be able to locate points of entry by sensing changes in the electric current.

Weaknesses: Electric fences share many of the same shortcomings as other systems, mainly the recurring issue of false alarms. Any objects that come into contact with the fence will lead to an alarm. Legality issues are another disadvantage especially if installed in populated areas, since accidental injuries may lead to complaints or lawsuits. Electric fences also have a critical vulnerability insofar that a power outage will lead to system failure. A backup generator is necessary as a contingency measure, which adds another layer of complexity in the installation process. The strong electrical current that flows through the fence makes it a fire hazard if installed next to greenery.

The issue with false alarms

Imagine if a person owned a security device that went off several times a day. Perhaps a passing animal triggered the passive infrared sensors installed in their home, which are integrated with a siren response. Maybe high winds are causing trees and other objects to move, raising a motion detection warning from their CCTV camera and sending them repeated real-time alerts to their phone. It is likely that given enough occurrences, they would not pay any more attention to these alerts, and thus would be unprepared for a response if one of them turned out to be a genuine security threat. High false alarm rates desensitize security personnel and property owners and lead to headaches for all involved. Given the density and proximity of Hong Kong’s properties, repeated activation of sirens can also be a great annoyance to surrounding neighbours.

When it comes to false alarms, no perimeter intrusion detection system (PIDS) in the existing market is infallible. Some devices may be more reliable than others, but even the most dependable PIDS have a sporadic false alarm rate, subject to variables such as changes in weather and lighting. Weekly, daily, and even hourly occurrences of false alarms are common within the scope of intrusion detection systems. As it stands, the rate of false alarms is hindering the growth of security devices in the market.[iii] Under these circumstances, experts are looking at methods to minimalize the false alarm rate if not completely eliminating it. One potential solution is the use of smart AI to filter out interference unrelated to actual intrusion attempts. However, despite the advancements within the security sphere in recent years, this technology remains to be perfected.

D-Fence pressure sensing system – another perspective on security

D-Fence is a perimeter intrusion detection system that uses pressure as its main method of detection. Currently, it is the only system within the market to do so. The core component within the D-Fence system is the pressure sensor, which converts force, pressure, weight into a measurable change in electrical resistance. The sensor is implemented into fences or walls which form the perimeter of a property. Any intrusion attempt heavier than the predetermined settings (i.e. 25kg), or any attempt to dismantle or neutralize any of the system components will immediately generate an alarm in the control center and will activate all the external systems connected such as CCTV cameras, lights, sirens, etc.

Strengths: The D-Fence system is particularly effective in cities like Hong Kong, where high value properties see a high demand in defensive perimeters needed to secure them. The pressure-sensitive sensors can be integrated with any outer perimeter/fence, and are completely concealed to the human eye. This gives two advantages: first, potential intruders will not realize that a security system has been installed within the premises and will be unable to arrange countermeasures; second, the outward appearance of a perimeter will not be affected. The main leverage that the D-Fence system has above all other intrusion security systems is a near zero false alarm rate (averaging once in three months). A 25kg pressure threshold eliminates false alarms made by small animals, falling branches, high winds, or anything other false positive that fails to meet the set requirement. This leaves cases of intrusions by humans (children and adults), or rare exceptions such as falling trees or boulders if the property is constructed next to a mountainside. D-Fence’s system also operates equally well in all weather conditions, regardless of rain or humidity.

Weaknesses: The D-Fence system’s installation and maintenance costs mean that it might not be the most practical choice for properties where appearance and security are not a top priority. To guarantee breach detection, D-Fence must also be installed along an entire perimeter. The system can be implemented in a partial capacity, but potential trespassers may be able to identify and breach exposed areas that are not protected by the D-Fence system.

Hong Kong going forward

Currently, the majority of estates and buildings in Hong Kong rely heavily on established modes of technology such as CCTV cameras and IR Sensors to deter and prevent intrusions. However, while they are considered satisfactory security measures, these devices are susceptible to false alarms which often lead to a loss in confidence by operators. If perimeter intrusion detection systems are to progress, false alarms must be reduced or eliminated and research is being done to achieve this, with new advancements such as pressure-sensing systems being conceived. Whether Hong Kong will decide to devote more resources to adapt to these systems remains to be seen, but one thing remains clear: The city risks losing its competitive market advantage if it refuses to embrace innovation.


[i] P.8,




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