IEC 61558-2-26:2013 deals with the safety of transformers, power supply units and switch mode power supply units all for saving energy and other purposes in electrical installations by adjusting the output voltage and/or other electrical characteristics on the output circuits without interruption affected by the transformers, power supply unit and switch mode power supply unit. The attention of National Committees is drawn to the fact that equipment manufacturers and testing organizations may need a transitional period following publication of a new, amended or revised IEC publication in which to make products in accordance with the new requirements and to equip them for conducting new or revised tests. It is the recommendation of the committee that the content of this publication be adopted for implementation nationally not earlier than 12 months from the date of publication. This publication is to be read in conjunction withIEC 61558-1:2005.