The phone has only one charging cradle via which the phone is charged. The router (in my case the Salt Fiber Box) takes over the task of the "base station". The router must be DECT-capable in order to be able to connect the HX telephones at all. The router (or already existing bases) determines whether the HX telephones work or not.
The Gigaset C570HX (and all HX phones) works alone together with a router that supports the Dect function.