IEC 61439-3:2012 defines the specific requirements for distribution boards intended to be operated by ordinary persons (DBO). DBOs have the following criteria: - intended to be operated by ordinary persons (e.g. switching operations and replacing fuse-links), e.g. in domestic (household) applications; - outgoing circuits contain protective devices, intended to be operated by ordinary persons, complying e.g. with IEC 60898-1, IEC 61008, IEC 61009, IEC 62423 and IEC 60269-3; - rated voltage to earth does not exceed 300 V a.c.; - rated current (Inc) of the outgoing circuits does not exceed 125 A and the rated current (InA) of the DBO does not exceed 250 A; - intended for the distribution of electrical energy; - enclosed, stationary; - for indoor or outdoor use. This first edition cancels and replaces the first edition of IEC 60439-3 (1990), Amendment 1 (1993) and Amendment 2 (2001). It constitutes a technical revision. This edition includes the following significant technical changes with respect to IEC 60439-3 (including the amendments): - alignment with IEC 61439-1:2011. This publication is to be read in conjunction with IEC 61439-1:2011.