Corrigendum 1 to Recommendation ITU-T G.8031/Y.1342 clarifies section 11.1 (APS format), section 11.2.1 (Principle of operation), section 11.10 (Equal priority requests), 11.15 (Failure of protocol defects), Annex A (State transition tables of protection switching) and Appendix IV (State transition diagrams using SDL).