This standard deals with all aspects of safety such as electrical, thermal and mechanical. This part 2-19 of IEC 61558 applies to stationary or portable, single-phase or poly-phase, air-cooled (natural or forced), independent or associated: - isolating transformers; - safety isolating transformers, having a rated supply voltage not exceeding 1000 V a.c., a rated frequency not exceeding 500 Hz, the rated output not exceeding 10 kVA, with a mid-point lead out in the output circuit for the purposes of attenuation of mains borne disturbances, and intended to the supply of office machines and the like. Perturbation attenuation isolating transformers: - shall have a no-load output voltage and a rated output voltage not exceeding 500 V a.c. or 708 V ripple free d.c. and exceeding 50 V a.c. or 120 V ripple-free d.c.; the no-load output voltage and the rated output voltage may exceed these limits in order to be in accordance with the national wiring rules or special purposes, however they shall not exceed 1000 V a.c. or 1415 V ripple free d.c.; - are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification. This standard is applicable to dry-type transformers. The windings may be encapsulated or non-encapsulated.