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Perimeter security design

When one starts to design a perimeter protection system you need to consider and evaluate the site, taking cognisance of international best practices, such as the four Ds for perimeter protection systems: Deter, Detect, Delay and Defeat.

Deter: This prevents crime by convincing the criminal that the target is too tough. Signs which notify passers-by of security measures are a deterrence. So are chain-link fences topped with razor wire, or patrols cars and armed guards.

Detect: If deterrence does not work, a criminal may attack the target and the detection layer notifies someone that an attack is occurring. For instance, a window contact alarm notifies the alarm company if the window is raised. Without a detect layer, the crime can take place and no-one is the wiser.

Delay: This is hardening the target with tougher materials such as property cages, security boxes, etc. A solid-core metal door and longer screws which connect the door frame to the walls is an example of delay because it will take longer to pry open than a normal door. Adding a padlock to the inside of a gate will add a delay layer. Delay does not mean “make impossibly strong”. All barriers can eventually be penetrated.

Defeat: Sometimes referred to as the response layer, this is what the police or security forces do – they catch the bad guys (or more often, run them off).

Before starting, the designers and installers will need to ensure that their plans are compliant with all local regulations as well as any site-specific regulations and processes. To establish this, one will need to conduct a detailed on-site survey of all existing perimeter security mechanisms and protocols to gather the information required. Thereafter one can start to design a solution based on the following considerations:

• Client concerns and issues related to the current system.

• Status of and age of the current system.

• Consideration of detailed site condition evaluation.

• Types of technology available.

• Technology performance and limitations.

• Site influences on-site which may influence technology choice.

• Integration of technology into existing system.

Types of perimeter security technologies

Video intrusion detection: Video is used and analysed through a digital signal processor to determine pixel change and apply a written algorithm to determine a potential threat or targets within the field of view. These systems normally consist of a number of cameras back-to-back with an overlap to cover dead lengths below the camera. Thermal and/or CCD cameras with an illumination source are normally used in this application along with software management systems that will alert the operator when a human target has been detected.

This system allows the operator to visually verify the cause of the alarm as well as providing additional situational awareness to make informed decisions when dispatching response teams.

Microphonic cable detection: The digital microphonic cable fence disturbance sensor will function as an electronic perimeter intrusion detector. This system is deployed on boundary fences or physical barriers to protect the perimeter of a site. This technology detects alarms caused by attempted cutting, climbing, or lifting of the fence structure.

Seismic perimeter detection: The seismic sensor is a covert intrusion detection system designed to generate an alarm when an alarm is triggered by digging, walking or running in the vicinity of the perimeter fence. Seismic sensors are normally buried and as a result are not easily located and avoided or tampered with.

Microwave detection: Microwave sensors generate an electromagnetic (RF) field between transmitter and receiver, creating an invisible volumetric detection zone. When an intruder enters the detection zone, the changes to the field are registered and an alarm is raised.

Non-lethal electric fence: Electric fences carry an 8 Joule pulsing electrical circuit and when touched by a person or animal, will deliver a shock. Should a person or animal cut, break or short the live and earth wires, an alarm will be created at the local energiser.

Human radar detection: Radar offers unique advantages over other sensors for the detection of humans, such as remote operation during virtually all weather and lighting conditions. However, humans are difficult targets to detect because they have a small radar cross section and move with a low velocity. Most current radar-based human detection systems employ some type of linear-phase matched filtering as part of the detector to improve accuracy and filter environmental influences.

Video management system: Whether new or existing, this is the heart of the system and to a large extent determines many aspects related to system design, including:

• Type of technology which can be integrated.

• Operator interface and usage.

• Remote access.

• Failover and redundancy capabilities.

• Anticipated life span of the system.

• Third-party system integrations.

Finally, the site will also need to consider the operators it will be employing in the control room to monitor and manage the installation. Do the operators have a good level of expertise related to the video management system and technology currently installed? Are the operators technology-savvy and do they have a good understanding of computers? Are the operators familiar with protocols and standard operating procedures on site? Is the present staff complement on site adequate for both day and night shifts?

XtraVision is an authorised importer and distributor of a complete range of fire and security technologies.

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