The Eartec Pro16 is a standalone wireless headset system.
Up to 16 headsets across 2 channel can be combined to work together without the requirement for a HUB.  
Pro16 headsets work on the 2.4GHz Licence Free band.
The operating range is quoted by Eartec to be ½ mile line of sight.
(Line of sight does not include wall/doors and other such obstacle).
N.B. It is not possible to interface PRO16 headset to a theatre wired intercom.