HX can be paired with various third-party base stations (routers), H can only be paired with Gigaset base stations.
See http://blog.gigaset.com/gigaset-hx/
No need for a button Just look here on page 9
https://gse.gigaset.com/fileadmin/legacy-assets/CustomerCare/Manuals/C43x-C53x/C430HX_C530HX/A31008-M2765-R101-2-4N19_de_IM1-AT-BE-CH.pdf
I bought the C530 HX and have successfully paired it with a C610 A. Compatibility is always one thing. In principle, many devices work together, the question is whether the desired features (internal calls, call waiting, weather display, ...) are usable. For my needs, simply making 0815 calls (via UPC and also via a SIP provider) is enough.
Hello CSperduto. I have connected my C530 HX to the Sunrise Internet box. It works perfectly. The phonebook, which is on the internet box, can be viewed and managed (create new entries, change, delete). The missed calls that my handset displays match the calls in the Internetbox list, so that works. Unfortunately, I can't say anything about the answering machine, as I don't use this feature. But I could imagine that standards will be implemented here and that this will work. But as I said, never tried it.
Best regards