Markdevoll,
Well I have never installed one of these as SIP is not that big in our market yet, but since it is a SIP Device it would require a SIP license. This also requires that you are SIP-DECT certified, which I am not, but I can download the documents if that will help you.
***Update***
I attached the installation guide for SIP-DECT 112.
Thanks,
TE