A word on isolation. This means that:The primary (240V) & secondary (115V) are totally electrically isolated (Dieletric isolation). This is the safest way of making a mains voltage conversion. We recommend this type of transformer whenever the application is medical or medically related or where the secondary equipment is to be operated in or near water or high moisture environments. Note the 240V earth is carried through to the 115V socket earth. As a further safety measure we now supply the ISOLATED units with resettable circuit breakers.