Tomographic Motion Detection

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What is it and how does it work

Well, how do traditional motion detection systems work? In the most basic form, a traditional passive motion detector has a defined FOV (Field Of View) utilizing thermal infrared energy technology.

When a source is in the FOV, thermal energy is emitted back to the motion sensor and it can detect changes against the background. Passive infrared sensors are the most widely used motion sensors in home security systems.

Once the sensor adjusts to room temperature, it can detect heat and movement in the surrounding areas, creating a protective “grid” detecting anything it is path has temperature related properties.Movie Rings (2017)Roblox Hack No Survey No Download

PIR Motion Sensor


Microwave motion sensors on the other hand senses detection by emitting electromagnetic radio waves either in a directional or omni-directional pattern cialis without a prescription. The radio waves will bounce off an object and back to the microwave sensor. The microwave sensor then reads the frequency of the returning radio waves which will vary depending on if an object is moving or possibly even by RF interference.

If an object is moving, the sensor will receive radio waves at different frequencies than the ones it sent out, signifying movement and setting off the alarm. Despite this, they are the least popular option on the market because of their vulnerability to electrical interference and their cost.

MIcrowave Motion Detector


TMD (Tomographic Motion Detection), is a technology that utilizes a mesh network of wireless nodes that sense a disruption utilizing electromagnetic waves that protect a defined security zone. Each of the these wireless nodes communicate with all other nodes in the network, thus creating a wireless mesh network. The interesting part of the technology is that the nodes have inherent RF properties that penetrate through solid materials making the system successful even when the devices are placed behind walls, boxes, and other non-metallic obstructions. This technology is much different than the traditional way of detecting motion when utilizing IR and/or microwave detectors. The most interesting aspect of this technology is that, not only can it detect motion, it can also locate the area where motion was detected. I also would like to point out you can’t change the laws of physics on RF properties, so there are some factors that must be taken into consideration on the design of a Tomographic Motion Detection System.


By definition, Webster Dictionary states, Tomographic is a method of producing a three-dimensional image of the internal structures of a solid object (as the human body or the earth) by the observation and recording of the differences in the effects on the passage of waves of energy impinging on those structures. Really? What does that mean? Have you ever heard of the term CAT Scan? The term CAT comes form Computer-Assisted tomography (Or just CT Scan).   TMD technology is a new way to detect movement (Motion Detection) that can be easily integrated into standard alarm system control panel equipment. As already mentioned, the technology uses wireless mesh networks that can penetrate solid materials making it much more efficient and reliable at detecting motion in a security zone than using traditional technologies (Motion Detection, Microwave, etc.).

A Xandem® TMD system ( is not a very complex system to install; the basic concept of the system is that there are two kinds of devices: A node and a processing unit (PU). A system integrator would install these nodes surround the area where motion is to be detected. Then, each node forms a powerful mesh network (As depicted in FIG 1. Below) with other nodes that emit RF energy called wireless radio waves (Radio Signals) that senses when objects move within the area of the mesh network; even when passing through walls and non-metallic obstructions.You can use the formula of N(N−1) to calculate how many links actually exist in a wireless mesh network. If for example, you have an 8 node system, there will be a total of 56 links in the wireless mesh network. As these nodes are transmitting and receiving radio waves, the received signal strength (RSS) of the transmitted wireless signals between the nodes are measured and the value is reported. The PU receives the reported values of the measured RSS and tracks the reported values over time. The PU then processes the reported values using a mathematical algorithm to detect motion and presence within the security zone. The final step in the process is that the PU will trigger an output relay to notify a connected control panel.

Xandem Wireless Sensor Node - TMDTMD Node


FIG 1.

Xandem TMD block Diagram Map


Operational Concept

The basic principle of Tomographic Motion Detection is when an object is in near proximity of a wireless communication link, and that object pass through the link, the radio waves will have been disturbed. This causes a change in the measured signal strength at a radio receiver. These changes in the characteristics of RF infer motion, presence, location, and quantity of objects.

As depicted in FIG 2., a person has entered the area of interest within sensor area (Radio Waves between Node A and Node B). The person’s body disrupts the radio waves as the person passes through and/or near the links of the wireless detection network (It is also important to not that there are waves emitting all around the node, so precaution must be taken when tweaking the nodes during installation). This disturbance results in a changed of signal strength (RSS Level of -53dBm to -65dBm) that can is measured at each receiver node (Remember, that Node A and Node B are receivers and transmitters [Transceivers]). This drop in signal strength is an indicator of detected motion. These measurements can be processed to infer the presence, motion, location, velocity, or speed of objects within the wireless detection network , and thus within the area of interest.

FIG 2.

TMD Diagram depicting two nodes

Due to the inherent nature of RF and it’s characteristics, understand that the signal strength of nearby links may change due to RF signal reflection, absorption, scattering, and possibly diffraction of the wireless signals around the object that has entered the area of protection. Also, due to multi-path reflections an object can cause on RF radio waves, the object does not need be located directly in the RF line-of-sight path of the transmitter and receiver and will more than likely cause a significant change in signal strength.

The mesh network of nodes that surround an area will each have a pattern when movement is detected and will create a different “signature” on a resulting link and aggregate disturbances will occur. Signatures can be trained into the system by walking in particular patterns/areas during installation or training periods.


  • Provides full-area coverage
  • Remains completely hidden
  • Prevents site reconnaissance by thieves
  • Sees through clutter and obstructions (including walls)
  • Is fully functional in dirt, dust, buildup
  • Is immune to birds, rodents, insects, temperature changes

The Nitty-Gritty Of It All

The technology is like a scene from a James Bond movie:

  • You can crawl on the ground, underneath desks, and slide against walls… but you can’t defeat a Xandem TMD
  • TMD is the only motion sensor you need for your alarm system. It doesn’t false trigger, and secures all.
  • Step into a TMD security zone and I guarantee you’ll step in jail.


It doesn’t matter if you can break through a wall, a window, ventilation system, from underneath the floor, or a skylight, a Xandem TMD solution will detect you; It is not a matter of when, how, who, or why, it is a matter of physics, which you can’t defeat!

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