Hi I am currently considering moving from 3CX running on Window 10 Pro to one running on Server 2012 R2. I have searched for information regarding 3CX's need for CAL's for each phone. I was reassured to conclude that it appeared that each phone does not need its own CAL. This information was rather old! However, I then checked 3CX operation system requirements and saw the following:- "Windows 2012 R2 Essentials (max. 25 presence connections on IIS installations)" So given that 3CX recommends using IIS on server based installations, does this mean that in Version 15 the phones do use a CAL when following this recommended option? If so, can this be avoided using Abyss option during installation and are they any drawbacks if doing so? Thanks in advance for any replies.