Abstract: An apparatus and method of binding serial numbers to thermostats to ensure that every thermostat in a large facility has a unique identification number. A Multi-Frequency Spread Spectrum technique (MFSS/AR) is used to select the suitable frequency for communication between remote thermostats and a centrally located controller. The MFSS/AR technique also uses an Acknowledgment/Retry procedure to ensure that each transmission is correctly received. In addition to reducing interference from other thermostats, the frequency switching used by the MFSS/AR technique also reduces the effects of background noise levels by selecting a clear frequency channel for a thermostat in a particular physical location.