The particular requirements of this part of IEC 60364 apply to the selection and erection of extra-low-voltage lighting installations supplied from sources with a maximum rated voltage of 50 V a.c. or 120 V d.c. NOTE 1 For the definition of an extra-low-voltage lighting system see IEC 60598-2-23. NOTE 2 AC voltages are given as r.m.s. values.