The "i" typically refers to a of QElectroTech. While the official QET project is excellent, several community-driven repositories use the "i" (Industrial) prefix to denote a version pre-loaded with industrial automation libraries—specifically Siemens, Schneider, and Allen Bradley.
Elias walked out into the morning sun, his headache finally fading. He had the library, he had the grade, and he had a valuable lesson in the chaotic, underground economy of industrial automation software. i qelectrotech siemens library free
Follow Siemens' naming conventions for devices (e.g., +CAB1-PLC1 for PLC in Cabinet 1). The "i" typically refers to a of QElectroTech