Outdoor security systems detect intruders as soon as a protected area is entered and before intruders are able to gain access to people or valuable objects and assets. Sensors can be placed in clear zones, e.g. open fields, around buildings or along fence lines. Exterior sensors need to be resilient enough not only to withstand outdoor weather conditions, but also reliable enough to detect intrusion during harsh environmental conditions. GIT-SECURITY.com is presenting a system invented by Sicurit Alarmitalia which will be showed also at this year´s Ifsec in Birmingham (10-13 May 2010).

Traditional and conventional exterior intrusion sensors have a lower probability of detecting intruders and a higher false alarm rate than their interior counterparts. This is due largely to many ungovernable factors such as wind, rain, ice, standing water, blowing debris, animals and human activity, as well as other sources including radio transmission interference. These factors often require the use of two or more sensors to ensure an effective and safe intrusion detection screen.

The product "Absolute Plus" from Sicurit is a high security dual-technology barrier that combines microwave and infrared technology to enhance detection capability while drastically reducing false alarm rates. Available in 3ranges (200/80/50m.), it consists of a pair (TX and RX) of extruded aluminum columns in which infrared beams and microwave technology are combined into one unit. Both sensing elements are located in a single casing, and are connected electronically using a special ‚AND‘ logic function. Since the two sensors will not detect an intrusion precisely at the same time the system has been designed to generate an alarm when both sensors produce an output within a pre-selected time interval.

"The sensors can be installed along a perimeter line, a fence or a delineated buffer zone, or as a defense against intruders approaching a gate or a wall", Sebastiano Vento, Export Manager of Sicurit Alarmitalia, explains. To further enhance information performance, image/video recorder equipment can also be installed to survey the intrusion or approach zone. In addition, to increase the detection potential, this capability permits security personnel to assess the nature of the intrusion alarm immediately and remotely.

Two Technologies - Maximum Detection

"The Absolute Plus alarm is the result of a sophisticated combination of the two most common and reliable technologies used for outdoor applications: active IR beams and microwave technology", says Sebastiano Vento. Surveillance is carried out by a temporary window memory circuit. The pilot circuits of both detection systems are equipped with a timer whose range is adjustable from 20 seconds to 2 minutes. The first device (usually the microwave, the activator) that receives a stimulus activates its own timer. Meanwhile, the second system is activated to confirm the final alarm. With this method of operation, nuisance alarms caused by environmental factors are completely eliminated.
The patented Sicurit synchronized, coded and bi-directional active infrared beams, the main innovation in this barrier system, represent a clear commitment to advanced research and development of forefront technology for perimeter security. A specialty of the IR beams is the bi-directional code transmission via optics with random secure-codes. Each optics transmitter sends a continuously modulated beam to the opposite receiver which is tuned to recognize only its own signal. Once confirmed, the adjacent optics (a transmitter) will then send back to its receiver a new secure-code.

Two-way Traffic

The bi-directional properties of the system enable IR beams to be totally immune to direct sunlight, often the cause of nuisance alarms in traditional infrared beam barriers. IR beams are also equipped with dedicated relay contacts in case of disqualification, only to inform the security personnel that the system is working as a traditional system using only the microwave detector for the disqualification period. The number of IR beams inside the column is determined by the height of the system and the application (high/medium security). Absolute Plus is provided with two IR beams by default, but up to eight beams may be added to each system.

Optional Extras

Microwave is the technology that functions as the ‘activator‘ because, in most cases, it is activated first. Its detection capacity is determined by a lobe that can be regulated with its own trimmer, reaching up to 8 m. in diameter. Moreover, as an option, ‘anti-crawling‘ Doppler devices can be installed in case there are no overlapping columns. This covers the blind area in proximity to the columns that the microwave's elliptical beam does not cover. Planar microwaves are used in models IMN050 and IMN080.

Absolute Plus columns can be equipped with built-in CCTV cameras. They are invisible and protected by a Plexiglas cover, and are therefore completely safe from atmospheric agents. A time record of the alarm sequences can be obtained by connecting a digital video recorder or a video transmission system via telephone lines. The video system can also be integrated with the site's main CCTV system by mounting a small camera inside the column to capture pre-alert pictures generated when the alarm is triggered.