I was at a home(for a social function) that has carrier zoning. They have 2 systems & each system has a master tstat located inside the conditioned area. There are several(what appears to be sensors) in the zones. Each sensor is only about 2 inches square with no means of adjustment. The temperature for each zone is set in the master tsat. You can turn a dial in the master tsat to select each zone. We will probably be servicing this system. Does any one have info on these? Thank You, Lee