Hello Steinma92,

The Gigaset N870 IP Pro are specially designed for Gigaset Pro DECT phones and are a multi-cell system.
This means that each station can take on different roles, which you can assign at the touch of a button.
The N870 IP Pro has an integrated DECT Manager as well as the roles as the basis for the DECT radio.
Therefore, technically speaking, the DX800a does not work. It is also important to note that you assign each handset its own call number, as you are in a different cell with each base, so the intercom with checkboxes is no longer possible as it used to be or is only available with the N510 IP Pro station, which is being replaced. (I am a Gigaset Pro Partner).
I therefore advise against installing a multi-radio system without specialist knowledge and appropriate training.
There is also not much in the user guide and all functions are assigned via Hosted PBX.
At the moment, the N870 IP Pro only supports the phones listed on the Gigaset Pro.
I hope I have been able to help and wish you all the best.
LG Youtec