Korg AX3G expression pedal?

[DWBH]

I have this effects processor, the AX3G and I wanted to make an EXP pedal for it.
However, how do I know how does the EXP pedal work? Variable resistance, or voltage divider?
It accepts both EXP-2 Foot Controller and XVP-10 Expression/Volume Pedal as expression pedals.
Where can I find schems for the fx processor, or for the exp pedals?

PS: I remember reading it somewhere that the Behringer FCV100 also works with it.