Abstract: A method and apparatus are disclosed for sensing, sampling and performing calculations on a parameter of a physical quantity at a plurality of remote locations comprising a plurality of remote sensing units and at least one processing unit linked to said plurality of remote sensing units via a two way communication link. Parameters of a physical quantity are sensed and sampled, calculations are performed and accumulated and transmitted, on demand, provided to the processing unit using a plurality of frequency bands one of which is identified as having valid data.