An apparatus and method for using a counter-propagating signal method for locating events is disclosed. The computing apparatus may comprise a set of interconnected central processing units. The user’s points of interest include at least one mobile point of interest, which periodically transmits its location. When the change rate \u03c6d is a positive value, the proportion \u03c9s1 gradually increases as the change rate \u03c6d increases. The cycle of output generation, conversion to sub-pixel resolution, and tone modulation selection is repeated iteratively until a desired gray level is reached. The reservoir is shaped and sized to fit below the motor housing, preferably in abutment, a portion of the reservoir being between the motor housing and the lower panel of the range hood.