I came across a 3 phase fan today at work, the starter is marked slow and fast but only contains three interconnected contactors with no other internal or external controls. There are six wires out to the motor ie three windings. I thought this is a mistake which should read for / rev so I asked someone to watch the fan asI tried it both ways and it is indeed slow / fast. I`m baffled, how is the speed changed with this contactor arrangement?.