remote audio control

I have been researching but can't find anything specific about the ability to control the audio levels & mix from a remote location. I don't mean from across the room, I mean from across the state. Does anyone know of a technology or company that will accomplish this? I've seen ethernet control that uses TCP/IP but couldn't find a definite answer where it could be used across the internet as opposed to intranet. Our studio is looking to have a master control studio where it can control several remote studios that will be scattered across the state, from the same location.

Thanks in advance,
-Greg