In some embodiments, the number of active cells in a multi-cell voltage regulator is controlled so that the current-per-active-cell approaches a predefined target or to be within an acceptable range so that the active cells operate with suitable efficiency. First and second discharge electrodes are provided in the ceramic multilayer substrate and face each other across a gap. If the calling party wishes to confirm the conversion, the text message is then converted to a voicemail message. The roller cone has a plurality of inserts disposed at selected positions about the cone. The non-aqueous organic solvent includes about 1 volume % to about 40 volume % of ethylene carbonate, about 1 volume % to about 50 volume % of ethyl propionate, about 1 volume % to about 50 volume % of diethyl carbonate, and about 1 volume % to about 40 volume % of propylene carbonate.