2005NEMA ICS 61131-1-2005 Programmable Controllers Part 1: General Information (Formerly NEMA IA 2.1)
1994NEMA IA 2.1-1994 Programmable Controllers - General Information R(2002)
NEMA IA 2.1-2005 Programmable Controllers - Part 1: General Information (National Adoption) was changed to NEMA ICS 61131-1-2005 Programmable Controllers Part 1: General Information (Formerly NEMA IA 2.1).