First of all you will need to have the Share Line Appearance application setup. See Click Here.
Prepare the Skype for Business/Lync User
- Make sure that Exchange UM voicemail is NOT setup for this user. (we want the caller to get Busy on Busy, NOT voicemail, right?)
- I might suggest to remove all delegates and team call members from the user you are going to enabled Busy on Busy, just to ensure no unexpected experience when enabling set-CsSlaConfiguration.
Now in Powershell we will very simply enable Busy on Busy for this user:
\>set-CsSlaConfiguration –Identity <skype4buser> –MaxNumberOfCalls 1 –BusyOption BusyOnBusy
Now place the 1st call to this user you just enabled Busy on Busy. This call should go through and connected. Stay connected on this call. (Placing the call on hold is fine, it is still considered a call to this user) and call this user again.
You will get a notice that the user is in another call.
This was tested on the Skype for Business client but not any other endpoints.
Also, this seems to work but I haven’t notice this officially mentioned as a supported scenario so try it out at your own risk, test it and give feedback if you find any problems with it.