• 25/05/2019
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A security system must detect threats as early as possible — that is a fundamental rule of security. If you have an outdoor area around your house, outdoor detectors should be installed there. In order to detect an intruder even before a door is opened or a window is broken, it needs to trigger the sirens and give a head start to the security company or the police squad on duty. As a result, it significantly increases the chances of preventing damages and protecting the health and lives of people.

The protection of a territory can be implemented in two ways. If the property is fenced and the outsiders are not allowed to enter, motion detectors with a wide horizontal view angle and detection range are used. This was precisely the device Ajax used to launch its range of outdoor security devices: MotionProtect Outdoor. Otherwise, in the cases where the detection zone needs to be limited, curtain detectors are used. They detect motion in a narrow zone preventing anyone from approaching a door or window, enter a terrace, or climb up a balcony unnoticed. They use an invisible curtain to fence off the territory where people can move freely.

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Wireless Ajax MotionProtect Curtain motion curtain detector

MotionProtect Curtain

Wireless outdoor curtain motion detector with anti-masking and pet immunity

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A unique motion detection system

Motion detection system is the key element of the curtain detector. The simplest detectors use only a single PIR sensor and a focusing optical element: a mirrors or a Fresnel lens. More expensive models are equipped with an additional microwave sensor to filter natural interferences.

Any warm object emits infrared radiation. A lens or a mirror focuses this radiation on a specific area of the pyroelectric sensing element (PIR sensor). When the object is moving, the radiation that it emits strikes different areas of the sensor and its intensity also changes. By analyzing these data, the detector decides if it is: a threat or a false alarm.

The “curtain” had to be able to receive more information about the events in the detection zone. Therefore, they adopted the approach used in the outdoor motion detector MotionProtect Outdoor: the system consisting of two PIR sensors. Only they were not narrow multidirectional “rays” but rather discrete “fan-shaped” zones:

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After assembling new test benches, the developers simulated the behavior of people, animals, birds, and all sorts of natural interferences in the lab. They changed the ambient temperature, studied the effect of speed and direction of movement, and then analyzed the data collected by the sensors. The results were highly promising! We now had a prototype of the optical system that enabled us to develop pet immunity.

Ajax MotionProtect Curtain

Segmented mirror of the MotionProtect Curtain detector

Four months into the development of the new detector, we had a suitable optical system. It offered a horizontal view angle of 6° and could detect motion at a distance of 11 meters. And most importantly, it collected sufficient data to tell apart a human from a pet or a bird and minimize the chances of false alarms triggered by natural events.

Professional-level anti-sabotage protection

Alongside the development of the motion detection system, we were working on countering masking. This is a typical sabotage tactic used with outdoor security systems: block the view of motion detectors (by covering or painting over the lens) when the system is inactive and then break into the secured premises unnoticed. Our curtain detector had to be able to detect such threats. The small dimensions of the body and the limitations in power consumption did not allow the installation of several pairs of IR emitters and masking sensors (there are three of them in MotionProtect Outdoor), so we had to think outside the box again.

Ajax MotionProtect Curtain

The tamper does not allow a disarmed detector to be secretly dismantled

The detector was also fitted with two tampers: the first one responds to the opening of the body, and the second one responds to attempts to detach the device from the SmartBracket mounting panel.

Combined with frequent polling of the detector by the hub that can identify the loss of communication with the device in less than one minute, these systems provide 100% protection against sabotage.

MotionProtect Curtain prototype and already working device in body printed on 3D-printer

ZOE algorithm

The basis for the development of the new software included SmartDetect and LISA algorithms used in the Ajax indoor and outdoor motion detectors as well as the understanding of how the optical system of MotionProtect Curtain “sees” people, animals, birds, and natural interferences. We collected 30 identical detectors and installed firmware with a draft version of the ZOE algorithm on them so that the devices could make decisions on their own with respect to which signal can be regarded as an alarm to be transmitted to the hub and which one to ignore as interference. And we have fitted them with special “black boxes” that retain all the original data in the detector memory when the latter are triggered.

The prototype detectors were tested at real premises located in Ukraine, Italy, Spain, Greece, and Cyprus: urban and suburban land plots, apartments, houses, and offices with the most unfavorable conditions that the curtain detectors could encounter. When the sun blinds the lens, the body is filled with rain, trees, bushes, and tall grass appear in the field of view, and animals of various dimensions continually trigger false alarms. Since it was summer, the R&D team moved into a giant industrial cold store with a temperature of -20°C for several days to test the operation of the device under extreme conditions.

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MotionProtect Curtain in a black body (indoor use only)

Over the course of a month, we perfected ZOE: we received false alarms, compared the data from the “black boxes” with the detection circumstances, introduced corrections to the code, and updated the software of the test devices. Each new version of the algorithm reduced the number of false alarms until we achieved absolute accuracy in human detection and effective filtering of interferences.

How ZOE operates

The motion detection system of the MotionProtect Curtain curtain detector offers two modes: with active pet immunity and without it.

When the pet immunity is enabled, PIR sensors represent independent data sources. Once in the detection zone, a person crosses two fans of rays provoking signals from two sensors with the characteristic symmetry and coverage. The ZOE algorithm instantly analyzes the data by comparing the parameters of the signals and reaching a verdict: intrusion. Animals, glares, leaves fluttering in the wind, air flows trigger signals of different nature, and the MotionProtect Curtain ignores them as false alarms. In this mode, the curtain detector can operate outdoors.

When the pet immunity is disabled, two PIR sensors operate as a single detection system: the MotionProtect Curtain is as sensitive as possible and has a maximum detection range. In order to trigger it, it is enough for a person to cross any of the rays. With allowance for the fact that the ZOE algorithm does not compare the character of the signals in this mode, the efficacy of protection against false alarms is lower. We recommend using MotionProtect Curtain with pet immunity disabled only inside the premises without potential sources of false alarms.

Fourteen months into the development, the second street motion detector, MotionProtect Curtain, appeared in the Ajax product range. With ultra-precise detection of humans, effective immunity to animals, and protection against false alarms. Operating indoors and outdoors and featuring anti-masking capabilities. With reliable and secure Jeweller technology and outstanding autonomy. Can be configured remotely through the app. Ready to secure an apartment, a detached house, and commercial or production facilities.

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