Hello.
Just to make sure that this post doesn’t fool others looking at it, Ring Intercom now supports properly Videx 901 (2-way calls from doorbell + unlock door).
Here is my installation:
As per app proposal, did the following wiring connections:
C1 → port 6
C2 → port 4
C3 → port 3
C4 → port 5
C5 → port 2
C6 → port C
C7 → port 6
Hope this may help someone.