An attachment assembly may be adapted for securing a panel member such as a class divider or a secondary door to a mating structure. The system resistance is utilized to determine a detection statistic indicative of current filter condition and to predict remaining life of the air filter. The Hadamard-transform output values are counted in each of a predetermined range of values and applied to an exponential frequency calculation to compute and update an average number of times that each output of the Hadamard-transforms falls into the corresponding predetermined range of values for a predetermined time period. A switch control circuit that switches a state of the switch unit between a conductive state and a nonconductive state is provided. Ideal toe-heel weight distribution can be achieved in this manner.