The present invention relates to foam control compositions and methods for controlling foam in aqueous media by adding to the system an effective amount of the foam control agent of the present invention. The function board and the voltage converter are connected such that a voltage generated by the voltage converter is supplied to the function board. The system further comprises means for changing the decay length of the evanescent field and means for correlating the detected signals with the change of the decay length of the evanescent field. The removable truck bed shelter may be constructed as an adjustable frame with an attachable cover or as a solid piece of weather-resistant material. The mask layer and the sidewall spacer are removed, to form a floating gate having a near-round edge shape.