Forensic Report: VDS video intercom system

Examination

Forensic Questions

What does it do?
The video phone serves the purpose of communicating with an external camera and microphone reciever, in order to show the user who is ringing the doorbell.

How does it work?
The Fermax Wi-Box works by connecting to the VDS video intercom system in your home, allowing calls from the doorbell to be forwarded directly to your mobile device. Using the free Wi-Box app, available on both Android and iOS, you can remotely manage the intercom system, answering calls, viewing live video, and even unlocking doors or gates from anywhere. The Wi-Box operates in parallel with the home’s internal monitor, providing seamless control over access to your property while you're on the go.

How it's built?
The FERMAX VEO Color 4.3" Duox Plus monitor is constructed using a combination of electronic and plastic components. The main body is made of plastic, providing a frame that houses the internal circuitry. Electronically, the device is equipped with a color LCD screen, which serves as the user interface, and a control board that processes incoming signals from the Duox Plus system. The monitor also includes integrated buttons for user interaction, and it is powered by a low-voltage electrical connection.

Why it failed, or it wasn't used anymore?
The speaker and microphone part of the machine did work. However, the screen and communications component unfortunately wasn't working. The circuit was probably damaged in an energy surge and therefore fried the microcontroller from the main body.

Steps taken

1. Cleaned the dust off the phone and brought it to the MDEF room
2. Disassembled each part (phone reciever and monitor) using our toolbox, while taking note of all the components that it is made of
3. The phone reciever was composed of these main parts:

• A speaker and a microphone

4. The monitor was composed of these main parts:

• LCD screen, microcontroller and input PCB to connect to the main wiring in the house.

5. After disassembling, we proceeded to try to manually make the parts work one by one.

Testing

After disassembling the intercom, we separated the different electronic components: the microphone, the speaker, and the screen. We then tested each of these circuits and examined them to understand how they work and how to make them function.

We did research on each of the electrical and electronic components in order to understand what was necessary to get them running. We used the multimeter to see if each component was still viable and afterwards used Barduino board to see if we could make them do things that they usually do respectivelly (pick up sounds, give off sound, or give off a graphic)

The first component to test succesfully was the speaker, which accompanied by a simple piece of code we were able to produce a simple song using tones.

After testing that, we proceeded to test the screen. Our first goal was to just make the screen light up, unfortunately we were not able to do so. Our theory is that there was an energy surge that fried the microcontroller of the screen.

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The last component to test separately was the microphone. With this we had some difficulty due to the fact that we could only find one piece of documentation about the particular amplifyer that the microphone was using, and even that differed with our own tests using the multimeter. We are still pending on seeing if the microphone is able to pick up sound or not. We did however gather a piece of code in order to test this in an objetive way.
So We decided to separate all the microphone components from its control board to recover the parts and try to get the microphone working by creating our own circuit. This way, we can attempt to connect it to the speaker.

This code works by printing the value of the intensity of the signal that the microphone picks up.

Results

How many motors did we find inside?
None.

Does it contain a computer or microcontroller?
Yes, one micro-controller that controls the screen and an other for the buttons and whic the comunication system.

Did you found any sensors?
It has buttons and a microphone.

Conclusions

What did you learn?

• How to power up each component individually
• Fundamental electronics
• The typical wiring needed for these machines to work in one's home or building
• Coding necessary to make the speaker produce tones and music

What surprised you?

• How complex a simple machine that is made for closed circuit communication can be.
• How much thought is put into just one part of the machine, specifically the reciever part which contained magnets and foam in order to improve the UX.
• The quantity of plugs a screen has.
• How much the 3D technology has improved since 2015

Images