This part of IEC 61347 specifies particular safety requirements for electronic step-down convertors for use on d.c. supplies of up to 250 V or a.c. supplies of up to 1 000 V@ at 50 Hz or 60 Hz and with rated output voltage ??50 V r.m.s. at a frequency deviating from the supply frequency@ or 120 V ripple free d.c. between conductors and between any conductor and earth@ associated with tungsten-halogen lamps as specified in IEC 60357 and other filament lamps. NOTE The limit of 50 V rated output voltage is in accordance with band I of IEC 60449. Particular requirements for electronic step-down convertors with means of protection against overheating are given in Annex C. Particular additional requirements for convertors providing safety extra low voltage (hereinafter SELV)@ are given in Annex I. Performance requirements are covered by IEC 61047. Plug-in convertors@ being part of the luminaire@ are covered as for built-in convertors by the additional requirements of the luminaire standard.