Seeing and listening through a wall: radio waves and optical fibers


A research team from University of Utah is at work on a project that allows usage of a small network of wireless radio transceivers, in order to detect movements of people on the other side of a wall.
Thanks to this detection system, based on the RTI (Radio Tomographic Imaging) concept which allows the images to be send via airwaves, police, surveillance forces and firemen will be able to detect intruders or casualties trapped inside a building, by simply placing these small transceivers in the area.

The RTI system is basically reading the “shadows” of radio waves when they pass through a person in motion, and based on these shadows it builds an image. In an experiment that has been used as an example, scientists have created a small network with 28 transmitters, placing them in rectangular shape in a room and in the garden outside the house.

At this point, the radio signal strength was measured, first when the rectangle was empty, and then with a person inside it. By transferring the relevant data to a computer with a calculation software, a very blurred image, resembling a shadow, is created by this software.
By improving method and detection systems, it has been possible to detect human movements on the other side of a wall.
The network used is not a normal Wi-Fi network such as the one normally used at home for computers, so it can not be detected by devices using such protocol, and can be used for surveillance purposes. The Zigbee communication protocol used for this system can generally be found in automated domestic appliances.

Since it is based on radio waves, it can also work in the dark, and due to the very blurred image that can be obtained, it does not pose any kind of threat under the privacy point of view. In order to obtain images with a better quality, an optimal solution is the usage of optical fiber devices, such as for example a fiberscope, made up of a tiny cable, only 2.5 mm in diameter, which carries a drill bit camera at one end.

Just dig a hole in the wall and insert the cable, and maybe connect the fiberscope to a digital video recorder to record high quality images inside a room. Alternatively, a non invasive option, used only to listen through the wall to what happens in the room nearby, is the usage of a wall microphone.

A wall microphone is basically a technologically advanced version of our doctor’s stethoscope, equipped with high sensitivity microphones and connected to a power amplifier, which makes it capable of listening through brick walls without arising any unnecessary suspicion or attention. Once again, in this case you can use a digital recorder to store any information or evidence gathered.

Candid camera (and not only) for everyone, with a pocket video recorder


When you spend a weekend outside with your friends, when you go to a concert, or maybe when you are at a lengthy work meeting or lecture, you might want or need to film what is going on around you, to save funny memories or important work information. In situations like these and many more, it might turn out vital to have a hidden camera with you.

Thanks to its tiny size and a weight of just 50 grams, its memory of up to 8 Gb with a replaceable Micro SD card, on which it is possible to store up to 320 minutes (or 40 minutes for each Gb) of video and audio footage, with a 640×480 resolution in AVI format, the Mini-DVR miniature digital video recorder is your perfect companion for adventures, leisure or work.

With its miniature size (just 58x22x20 mm), it can be comfortably and easily taken along with you, and concealed inside the front pocket of your jacket, to provide high-quality covert recordings, for example for shooting candid camera videos, or as a convenient support to gather evidence during an investigation, either for private detective agencies or for law enforcement agents.

Furthermore, the Micro SD memory card can be easily removed and replaced, and its content can be easily downloaded on your PC. Mini-DVR is powered by an embedded rechargeable lithium battery, which allows for a maximum continuous recording time of approximately 100 minutes, making this pocket digital video recorder very useful also for long-term surveillance operations.

Talk on the phone, while filming what is going on around you

Bluetooth DVR

In the audio and video surveillance field, it is vital not to cause any kind of possible suspicion in the people being kept under observation. To achieve this, it is important to provide yourselves with tools that allow gathering of information in a discreet way and without arising any unnecessary attention and which do not obviously look like a recorder, a hidden microphone or a videocamera.

And this is exactly when a Bluetooth earphone DVR might turn out useful. At a first glance it looks just like your ordinary earphone, but on the inside it contains a miniature video camera with an embedded video recorder. This hidden camera is capable of recording videos in 640×480 resolution, which are saved on the embedded USB memory card with a 4 Gb capacity.

This results in the possibility of storing up to 2 hours of video footage, to be downloaded on your PC via USB cable. The lithium battery allows for a maximum continuous recording time of approximately 100 minutes.

A device like this is perfect for situations where privacy is a must, for example evidence gathering by law enforcement or detective agencies, Just clip it on the front pocket of your jacket or shirt, or on your trousers’ belt, and you will be able to start recording with just one touch. Other possible options include recording during concerts or lectures, or point-of-view recordings during a bicycle race or a ski downhill.

In short, you can use this miniature video camera in a million ways, even as… an earphone for your mobile!

Hidden footage, recorded with your car’s remote control

DVR Remote

When you need to capture what is happening around you on video, be it for work, for leisure or for legal reasons, you may find yourself in condition to do it as discreetly as possible, so as not to raise unnecessary attention and suspicions. Therefore, the job must be carried out by using a device that is as small as possible and that does not look like a video recorder or a hidden camera.

For example, you might use something like a remote control videorecorder. No, we are not talking about using the remote control of your home VCR, but about a tiny device that at first sight looks just like the remote control of your car alarm, but on the inside conceals a miniaturized digital video camera, capable of recording up to 2 hours of video footage, which is then stored on the embedded USB memory card, with a 4 Gb capacity.

Thanks to this miniature video recorder, you will be able to shoot video recordings with hidden camera, with a 640×480 resolution in AVI video format, and download them into your computer thanks to the USB cable. The maximum duration of the lithium battery is up to 100 minutes in continuous recording mode.

Thanks to its small size and its ease of use (recording can be starting by just pressing a button), it is a perfect tool for shooting candid camera videos, to save a live concert, as well as for gathering evidence to be used on trial or before a court of law, or to take notes during an important work meeting or conference; your fantasy is the limit!

Ah, by the way, in case someone is wondering: aside from all this, it can be really used as a remote control for your car alarm!