Symptoms
When you make an outgoing public switched telephone network (PSTN) call from lync room system (LRS) with other users in Microsoft Skype for Business 2016, a Dial pad UI shows up unexpectedly in the Front of Room display with "Hold", "Transfer" and other options available. Transfers aren't supported in LRS, so this UI should be blocked. In previous builds, LRS shows up a Dial pad static image instead of the dialpad itself.
Resolution
To fix this issue, install the December 6, 2016, update (KB3127980) for Skype for Business 2016.
