Intruder Detection

INTRUDER DETECTION

An intruder detection system generally falls in to one of two distinct categories, domestic and commercial. The system’s basic functionality is to detect unauthorised entry to a building. Although external intrusion detection systems exist, this page only refers to internal systems.

The systems are designed to detect an intruder, identify the location and signal the activation. Detection, control, and reporting devices are the basic components of a burglar alarm system. Sensors detect an event. A control panel coordinates how the system responds to sensors and identifies the location of the sensor originating the signal. Local annunciators and remote communications devices allow system activity to be reported.

Domestic intruder alarm systems are generally limited to contacts, passive infra-red sensors, and in certain situations, beam detectors or break-glass detectors may be applicable.

Commercial systems have different requirements, since the security risk may be greater depending on the value of the property being protected. Often the insurance company will have an influence on the level of security required.

In the UK, intruder detection systems are graded to EN 50131 which governs the design, installation and maintenance of intruder detection systems.

The range of sensors which may be applicable could be door or shutter contacts, passive infra-red sensors, or various ranges of multi-sensors using a combination of passive infra-red and microwave, vibration and break-glass sensors etc.

In certain situations, ancillary equipment may be specified such as smoke machines. These flood specific areas with dense smoke in order to make it difficult or impossible for intruders to operate. Commercial intruder alarm systems often operate in conjunction with CCTV systems, access control systems, and even as part of a major integrated system.

OPERATIONAL REQUIREMENT

In order to maximise the benefits of your intruder detection system it is important to establish some basic criteria as a starting point for the system design. The first of which is to define the problem and consider if intruder detection is the most appropriate response. Given that the answer is “yes it is”, it is critical to establish the operational requirements (OR) of the system.

The basic model for an OR is to establish the following information…

Site Plan – to identify areas of concern.
Statement of the Problem.
Stakeholder Liaison.
Risk Assessment.
Success Criteria.
Determine the Technical Solution.

With the OR in place it is then possible to design the most appropriate intruder detection system solution taking in to consideration that authorised personnel should not be impeded from their routine activities.

Level two of the OR should establish each portal to be monitored along with specific requirements such as emergency exit, manual override, time zones, alarm conditions and response.

Finally, the response to the intruder detection system needs to be considered. Who will monitor it, where from, what training do they need etc.

SYSTEM DESIGN

There are many technologies available that detect intruders.

Magnetic Reed Switches
Break-Glass Detectors
Vibration Sensors
Passive Infra-Red (PIR)
Combined PIR/Microwave Detectors

These devices are placed around the building in strategic locations in order to form zones and areas, allowing the zones to be set or unset depending on how the user wishes the system to function.

A keypad is used for programming, setting and un-setting the system.

The controller is the central processor of the burglar alarm system. It receives information from the sensors. When it receives a signal indicating an abnormal condition, it activates the reporting device, whether it is local sirens or remote monitoring.

The controller also monitors the state of the system and reports accordingly.