the additional ring may be for a mono microphone.
I think you're right. Since my last post, I have located an adapter that is Male TRRS to two Female TRS, one of which is for a mic input and the other for iPad audio out.
I'm going to do a bit of research to see just what my old Apple mic is - electret or condenser. I'm hoping I have an electret as the adapter specifies the mic input is only for electret (ECM).
This is the microphone if anyone knows the answer.
