The Gigaset Comfort 500 A Duo (CH version) is basically compatible with the Swisscom Internet Box 4, as it is an analogue landline telephone that can be operated on the analogue connection of the Internet Box. However, it does not work via DECT, but via the analogue connection, which is why not all the advantages of digital DECT technology can be used. The basic telephone functions should work correctly, but advanced DECT functions of the Internet Box are not available.