The MH1 is OTMP rather than CTIA.
What this means is an MH1 will sound terrible when plugged into a modern Android device, but will sound normal when you press the middle button. An MH1C will sound normal, button pressed or not. The other way around for older Nokia phones and Sony Ericsson phones.
Ok thanks. I'll try and find some suitable phones to test it out.
Hmm both of my pairs had/have the Sony logo, not the Sony Ericsson one...