A portable computer having a display unit coupled to a base. The cell accurately determines the BrAC of a prospective vehicle operator. The second control element comprises an inlet that receives fluid, and an outlet that divides the fluid flow into at least a first portion and a second portion. The heater structure comprises a relatively resistive annulus of semiconductor material enclosed between an inner disk and an outer annulus of relatively conductive semiconductor material. A second hook assembly includes a second hook adapted to receive a second associated attachment pin. A bottom portion of the wiring layer is protected by the conductive barrier layer and the insulating barrier layer.