<quote>
A "Private Call" is a trunking term to mean two radios are communicating with each other, as opposed to on a talkgroup. In this case, the Ambulance dispatcher is communicating directly with an ambulance in private.</quote>
Mike has it correct, the Private Call is the dispatch centre initiating the trunking version of the Private Call (the button is labelled that on the screen) to communicate directly with the unit. Some dispatch centres use it, some don't. In Muskoka they used to use it quite a bit, but that seems to have trailed off.
Back when I had my older Pro-2052 scanning Fleetnet, I was able to listen to the Private Calls as they would come up as a talkgroup when you were "searching", but I'm not sure if the newer stuff still does that (as we generally enter in the talkgroups we want to hear and scan.