One of the coolest benefits IP PBXes can bring users is the ability to deal with calls via their computer screens. Instead of pressing a sequence of keys and then an extension number to transfer a call, for example, users can simply drag the image representing the call to a box representing the colleague. Open source IP PBX vendor Fonality Inc. has long offered such capability to regular callers via its so-called heads-up display, or HUD. Now it's extending HUD to an entirely new area: the call-center and conference-calling functions of its PBXtra and trixbox Pro products.
Read more about it here.