I have CUCM 7.1.5 with a lot of CIPCs connected to it. Each CIPC has 3 directory numbers (for example 107, 207, 307) and incoming call can arrive on any of these lines.

I have managed to allow only one call for each line by setting Busy Trigger = 1 in settings of each directory number.

What I want to do, is to allow only one call for the whole device (for all lines together). That is, when phone is already answered call from line 107, then if call is arriving on 207 or 307, CUCM should put 'busy' signal to new caller.