Unity does not control or change the CLID. This is done by the phone system. So for example, when placing a supervised transfer, Unity will place the caller on hold and make a consultation call to the transfer target. During this consultation call, Unity is the calling party. Thus most phone systems will display the Unity port extension number as the calling party on the destination phone.
If the supervised transfer returns due to RNA or Busy, the original caller is taken off hold and can leave a voice message. Unity will use the original callers CLID for this message.
If the supervised transfer is successful, Unity will release the transfer. The phone system will then connect the original caller with the transfer target. At this time, many phone systems will update the display at the target phone to show the original callers CLID as the connected party.
-Eric
