Frames of data are received. Each frame includes at least a sensor identifier and a changeable data field and is sent from one of a plurality of sensors. Each of the plurality of sensors is associated with a respective one of a plurality of sensor identifiers. The changeable data field includes, in some of the frames, data representing a sensed condition and, in others of the frames, counter data. The counter data is analyzed to determine whether any of the sensor identifiers can be associated with one of a plurality of sensor locations.