longer certified line-voltage appliances for bathroom use. Newer appliances had to use a step-down transformer to operate at low voltage (typically 12, 16 or 24 volts). Wiring standards in many countries require that outlets in bath areas must be protected by a RCD/GFCI device (e.g., required in the US since the 1970s on bathroom outlets in new construction). By the 1990s there were problems with safety certification of Broxo's original design. Further, improved battery-operated toothbrushes were providing formidable competition. The first ultrasonic toothbrush, first called the Ultima and later the Ultrasonex, was patented in the US in 1992, the same year the FDA gave it approval for daily home use. Initially, the Ultima worked only on ultrasound, but a few years later, a motor was added to give the Ultrasonex brush additional sonic vibration. Today, several ultrasonic toothbrushes simultaneously provide both ultrasound and sonic vibration. In more modern times, electric toothbrushes have been used as a substitute for vibrators for those who wish to avoid embarrassment. The negative environmental impact of electric toothbrushes when compared with manual toothbrushes has been established. Types Electric toothbrushes can be classified according to their type of action: Side to side vibration, which has a brush head action that moves laterally from side to side. Counter oscillation, which has a brush action in which adjacent tufts of bristles (usually six to 10 in number) rotate in one direction and then the other, independently, with each tuft rotating in the opposite direction to that adjacent to it. Rotation oscillation, which has a brush action in which the brush head rotates in one direction and then the other. Circular, which has a brush action in which the brush head rotates in one direction only. Ultrasonic, which has a brush action where the bristles vibrate at ultrasonic frequencies (> 20 kHz). Ionic, which has a brush that aims to impart an electrical charge to the tooth surface with the intent of disrupting the attachment of dental plaque. For some vibrating toothbrush designs, a brushing technique similar to that used with a manual toothbrush is recommended, whereas with brushes with a spinning head the recommended cleaning technique is to simply move the brush slowly from tooth to tooth. Electric toothbrushes can also be classified according to the speed of their movements as standard power toothbrushes, sonic toothbrushes or ultrasonic toothbrushes. If the motion of the toothbrush is sufficiently rapid