I tried this with Archaicarcane's help ---- an excellent blog tutorial:
http://www.archaicarcane.com/singerattheraces/ for an unresponsive foot controler.
There is also this, maybe, sewbeadit, this is what you were thinking of?
http://www.archaicarcane.com/what-a-pile-of/ (carbon buttons..... )
Archaicarcane is a valued member of this forum.