An improved band-gap voltage reference apparatus and method is detailed that incorporates an amplifier to provide for improved compensation and temperature stability to the voltage reference circuit by increasing the effective hFE of the bipolar junction transistors used in the band-gap voltage reference circuit. At least one of the two above-mentioned ratable elements has a plurality of undercut regions ) at the location of the centering walls. At least one of the two polarizers is a structural birefringent polarizing plate. The secondary cellular device remains activated, and provides a low-cost remotely accessible communication link between the on-board vehicle computer and the primary cellular device or any other phone, provided that specified security conditions are satisfied. By way of example, the state of the dialog may be quantified as: the internal state of the natural language understanding part of the dialog system; or words in the prompt that the dialog system played to the user. Further, the safety in use of the vacuum cleaner will be improved.