Corrigendum 1991 Covers the constructional, dimensional and test requirements for insulated aerial bundled conductors (ABC) of two or four core construction, having conductors of equal size and type in conductor sizes ranging from 25 sq.mm up to and including 95 sq.mm and having a voltage rating of 600/1000 V. The provision of insulated control or street lighting conductors is permitted and is detailed in Appendix B.