Tua Viso is safe. It is powered by a normal 8.4 Volt alkaline battery, which comes with the unit already fitted. The battery is held in a special compartment and easy to replace. A yellow LED indicator on top of the Tua Viso unit shows when it is time to charge the battery. You can read about battery-change in the Tua Viso Handbook or see the battery-change link on our online video, featuring Tina Richards ..... Click here to view video demonstration.