I've seen a fair few of those
and I've never worked them out. my aunt has one, but it always seems to flush the same no matter whether you press one or other button or both together
( Jadeviper was still alive on, Fri 8 Jul 2005, 14:58, archived)

The ones in Biblos work :P
My Grandmother has one where you lift up and drop immediately for a half flush, lift and hold for full, dead easy.

The Eden project in Cornwall have loads of different types in use, they're great :) Most of those also use reclaimed water. Good stuff :)
( Dekazer, Fri 8 Jul 2005, 15:03, archived)