What does it need to build a Window?

A single board computer:

- Raspberry Pi 3
    https://de.rs-online.com/web/cp/8968660,8968664/
+ Heatsink
    https://de.rs-online.com/web/p/kuhlkorper/8679039/
+ Power Supply
    https://de.rs-online.com/web/p/steckernetzteile/9098135/
+ SD Card 4 gb, UHS-1
+ a raspby case

RaspiCam with widle angle lense + IR filter:

cheap china: https://www.waveshare.com/rpi-camera-g.htm
medium/fast china: https://www.waveshare.com/rpi-camera-g.htm
expensive germany: https://www.comtech.de/raspberry-pi-kamera-modul-5-megapixel-mit-weitwinkelobjektiv-fuer-b-pi-2-pi-3-rb-camera-ww

USB Speakerphone with built-in echo cancellation

https://www.jabra.com.de/business/speakerphones/jabra-speak-series/jabra-speak-410?gclid=EAIaIQobChMI-ZO09riM2AIVSyrTCh0MdgKxEAAYASAAEgKzWfD_BwE

Ethernet cable

with some internet (>1 MBit Upload recommended). (do yourself a favor and skip wifi :)

HDMI Monitor:

you can choose between many models and brand bt take care of: - No standby function (has to turn on automatically on power-up) “Public/Info-Displays” might be better for non-stop usage - possibility to remove the feet - monitor tecnology IPS for better quality

1 Button

http://www.arcadewinkel.nl/de/steuerung/aktionstaster/concave-klassischer-aktionstaster-chrom (METAL) or http://www.arcadewinkel.nl/en/controls/pushbuttons/concave-classic-pushbutton-red (PLASTIC)

Frame for the Display and Camera

wood, metal or whatever you imagination can think of

Other options under experimentation:

Audio It is a BIG deal,during these two years of research we also found another cheaper solution, but further testing is needed: