Hello,
I have the same kind of issue with my intercom.
This is a variant of a Bitron Video AN0002, analog version, with only 2 wires.
Opening is done via short circuiting the 2 wires.
“Ring to open” do not work as when the intercom rings, I have a voltage of around 0,7V and Nuki do not manage to distinguish what is happening.
Here is some more details of my configuration: Analog intercom with 2 wires compatibility?
Feel free to add some comments.
Damien