Question: what is the difference between rj11 and rj9?
Answer: The difference is that RJ11 uses four internal wires (called conductors) while RJ12 uses six. RJ12 is backwards compatible with RJ11, but RJ11 will not work with RJ12. Coiled handset cords use a smaller connector called RJ9 or RJ22 (both names refer to the same thing).