This part of IEC 61558 deals with the safety of shaver transformers, power supply units incorporating a shaver transformer, and shaver supply units. Shaver transformers incorporating electronic circuits are also covered by this standard. NOTE 1 Safety includes electrical, thermal, mechanical and chemical aspects. Unless otherwise specified, from here onward, the term transformer covers shaver transformers and power supply units incorporating shaver transformers and shaver supply units. This part is applicable to stationary, single phase air-cooled (natural or forced), independent or associated dry- type transformers. The windings may be encapsulated or nonencapsulated. This standard is applicable to transformers and power supply (linear) with internal operational frequencies not exceeding 500 Hz. This standard used in combination with Part 2-16 for switch mode power supply units (SMPS) is also applicable to power supplies with internal operational frequencies higher than 500 Hz. Where the two requirements are in conflict the most severe take precedence. The rated supply voltage does not exceed 250 V a.c., and the rated supply frequency does not exceed 500 Hz. The rated output is not less than 20 VA and does not exceed 50 VA . The no-load output voltage does not exceed 275 V a.c and the rated output voltage does not exceed 250 V a.c. This part is not applicable to external circuits and their components intended to be connected to the input and output terminals or socket-outlets of the transformers. Transformers covered by this part are used in applications where double or reinforced insulation between circuits is required by the installation rules for bathrooms and similar locations, or by the appliance specifications. NOTE 2 Transformers covered by this part may be flush or surface mounted or incorporated in luminaires, mirrors, and other equipment containing one or more socket-outlet(s). NOTE 3 Attention is drawn to the following: - for transformers intended to be used in vehicles, on board ships, and aircraft, additional requirements (from other applicable standards, national rules, etc.) may be necessary; - measures to protect the enclosure and the components inside the enclosure against external influences such as fungus, vermin, termites, solar-radiation, and icing should also be considered; - the different conditions for transportation, storage, and operation of the transformers should also be considered; - additional requirements in accordance with other appropriate standards and national rules may be applicable to transformers intended for use in special environments. NOTE 4 Future technological development of transformers may necessitate a need to increase the upper limit of the frequencies, until then this part may be used as a guidance document.