One cable, the hoisting cable, runs from the forward end of the catchwagon, up the lift hill, partway down the drop, down beneath the lift hill, then back through the lift structure, through the tension wheels, and to the cable drum. When the train goes up the lift, this cable is wound onto the cable drum.
The other, smaller cable, runs from the back end of the catchwagon, down the lift hill, through the station, around a pulley, doubles back under the station, and attaches to the cable drum. This cable is wound in the opposite direction from the main hoisting so that as the catchwagon is drawn up the hill, the hoisting cable is wound onto the cable drum. At the same time, the other cable is UNwound from the cable drum. So the distance from the cable drum, to the station, to the back of the catchwagon, to the front of the catchwagon, to the top of the hill, and back to the cable drum remains constant.
I hope that makes sense! :)
--Dave Althoff, Jr.