Zone or Radar
Not too sure about Pierres answer. I am a 'Zone' controller and am also confused.
Lets see if I can clarify. All transit traffic whether through the MATZ or otherwise at our unit is controlled by the radio callsign XXX Zone, this is true whether the zone position is manned or whether the task is being fufilled by the approach controller. however on the landlines each controller identifies themselves as the position from which they are operating, ie. XXX Zone, or XXX Approach for Zone, or XXX Sup for Zone or XXX Director for Zone.
Where the term Radar is used in the radio callsign is when controlled airspace is involved. For example Brize Radar. From my understanding they have up to three controllers working transit traffic. LARS 1, LARS 2, and Zone. LARS 1 and 2 (if manned) deal with traffic transiting the local area on a north and south dividing line. If a track wishes to transit the class D around them they are transferred to the Zone controller, however all controllers have the radio callsign Brize Radar but when answering landlines refer to their control position either Brize LARS 1, 2 or Brize Zone depending on the manning.
Hope a) thats correct. and b) it helps.
As a pilot if you call all mil units XXX Zone apart from Brize Radar, you shouldn't go far wrong.
:Standing braced for BZN Controllers to shoot my theory down in flames: