@Graham
thank's for feedback
>... What does Internal mean?...
Internal calls between two home stations, for example:
call from HD Davos 203 to non Swisscom DECT phone on 204
or
call from HD Davos 203 to IP phone on 221
etc
>... It is not important, but I'd just like to know where I have got it wrong....
it does not seem that there is a configuration error, however it is possible that the desired function is simply not available
>... The Davos is has FW VH034....
The current version of the HD-Davos is indeed the FW vH034, it dates from the year 2020, these devices automatically receive a new version of the software when it is available, this is done through the internet-box, check in the managements of the router that the Firmware version is up to date