Skype for Business, Call Controls and IP Phones
Call controls are disabled on the Skype for Business client when answering a call with an IP Phone that is tethered via USB.
Call controls are disabled on the Skype for Business client when answering a call with an IP Phone that is tethered: This is the expected functionality of a Lync Edition IP Phone that is “tethered” or connected via USB cable to a Windows machine running the Skype for Business/Lync client. If you unplug the USB connection from the IP Phone to the computer then the Windows client and IP phone will not sync together. It will ring both end-points separately and once you answer the call on one end-point, it will go away on the other end-point. If you prefer to continue using call controls on the Windows client, then you have to answer the phone using the Windows client using a headset.
Note: if you chose to untether the IP Phone, you will no longer have the connection to Exchange, which provides information on the IP Phone like your next meeting.