The Gigaset DESK 800A can be connected to and used with a FRITZBox, including the FRITZBox 7530 AX, but with some restrictions.

- The telephone is a wired landline telephone and must be connected via an analogue telephone line, which is possible with the FRITZBox.
- To use VoIP functions or an integrated configuration with the FRITZBox, specific settings must be made as described in the case of the Gigaset DX800a, but this does not apply directly to the DESK 800A as it is not a VoIP phone.

Overall, the Gigaset DESK 800A can be operated via the analogue telephone line on the FRITZBox 7530 AX, but it does not use the specific VoIP functions of the FRITZBox.