Circuits, methods, and apparatus for protecting devices in an output stage from over-voltage conditions caused by high supply and input voltages. A passive RFID transponder is incorporated into the structure of the cart which when interrogated by an associated reader, located at the cashier’s check out station, responds with a signal verifying the presence, or absence, of an unseen item upon the carts bottom tray. An electric melter furnace is utilized for receiving intermediate carbon-containing metallized iron from the pre-reducing step, which is fed directly and continuously into a central interior area of the electric melter, with heating of the carbon-containing metallized iron in the electric melter under elevated temperatures of about 1300 C. A lid is included to cover the opening of the pan and forms an air tight seal around a perimeter of the pan opening. In the preferred embodiment, saliva production is stimulated by means such as breath mint or tart solution and the effect of dilution controlled by reference to albumin.