First I paired this handset to my already existing database (SL780), which is no problem, but against missing functionality (no DECT eco mode, no call log, no answering machine, etc.). I thought I had maybe update the firmware of the handset, but not because it was already up to date! And then the QuickSync software eventually suggested I update the firmware of the base of the SL910 ... And then I decided to try to redo all my installation this basis rather than the SL78.
Which solved my problems missing features: it is absolutely his small base to function properly, as it also has a firmware !!! And that is not a problem for the SL78 handset, which works fine on the basis of SL910 (ie, so that the reverse is not true).
The only big negative point (! But then prohibitive for me) is the QuickSync software: Despite a beautiful address book everything well organized, with lots of fields on Outlook, you can not synchronize contacts !!! The software definitely does not communicate with Outlook, and I do not want to create a Google account. It is a shame on the part of a firm as Gigaset (after Siemens still!) Not to be able to develop an app that is both functional and ergonomic (it can, simply).
Edition 07.09.2014
To synchronize contacts between the phone and the computer, Windows contacts works! To synchronize with Outlook, save the contacts as a vCard (.vcf) can import these Vcards (still on the computer) to the .contact format with Windows Contacts. The synchronization will then be perfect ... It's a pity, the owner of an Iphone, it loophole through Outlook and Vcards and Windows contacts to get to synchronize the smartphone and handset directory !!!