Below on this page are photos of a model train power pack made in England that has two totally separate rheostats (wired independently) to control two model train engines.
The rheostats are unique in that they are what I call "bidirectional rheostats" meaning that they can be rotate either clockwise (as rheostats usually are) or these can be rotated counterclockwise. (There is a middle "OFF" position ("12 o'clock") where the power is not sent to the track.)
The effect is that when the rheostat is rotated clockwise, the model train engine moves forward (left-to-right). When the bi-directional rheostat is rotated counterclockwise, the model train engine moves backward (right-to-left).
The advantage of this is that no "reversing switch" (D.P.D.T.) is needed to reverse the train's direction which means that operation is simpler, easier, and more intuitive for new users.
This power pack also uses pulse power which it calls "Half Wave" (which at the moment I am not interested in using). It also uses a selinum rectifer to allow the user to have more precise control over the movement of the engine which I am very interested in using. (By the way, there are two complete systems inside this power pack - i.e. two separate rectifiers, two separate bi-directional rheostats, etc.)
I have removed the rheostat from the right side of the power pack. I plan to remove both rheostats and use them by themselves (without the transformer in the power pack. I will power them with two separate power supplies.) I do not plan to use the transformer that came with the power pack.
However, I would like to use the selinum rectifiers that came inside the power pack.
Here are the photos: