A system to be installed on a merchandising unit having one or more inventory zones, one or more units of product, one or more product sensors, a mounting structure, and an electromagnetic signal processor. The one or more inventory zones can present the one or more units of product in several different arrangements. The one or more product sensors, each at least associated operatively with one of the one or more inventory zones, converts a sensed quantity of the one or more units of product into a respective analog electromagnetic signal. The mounting structure secures the one or more product sensors to the merchandising unit relative to the one or more units of product so that the one or more product sensors sense a quantity of the one or more units of product. The electromagnetic signal processor in communication with the one or more product sensors can sample output from the one or more product sensors periodically and converts the analog signal into a digital signal.