A display support system for releasably supporting a plurality of product-containing containers for display and sales of the products contained therein. Provided around a prechamber is a magnetic shield for the purpose of intensifying the magnetic blowing action on an arc formed between the arc guide rails of the prechamber. With the use of this technique, signal cross talk is minimized while enhancing NOx sensing sensitivity. Upon successful authentication, the sensing device is registered in the server so as to be associated with the printer. The sleeve may also be moveable to increase the control of the loop size and position, to facilitate greater control of the placement of the catheter tip.