Continuous loop or drag lure propulsion systems?

There are two types of lure propulsion systems, continuous loop and drag.

Continuous Loop
In a continuous loop system, the lure is tied to a string that travels along the ground like a belt. The lure is attached to the belt and typically travels down the center of the course and stops at the catch pen. It then is moved out the back of the course, around pullies that take the lure outside the course and back to the starting line. In current usage, the lure is powered by an alternating current motor.  The lure operator simply returns the lure out the back of the course and back around to the start. 

The problem for the dogs is that there needs to be a “return string” that follows the lure. The dog can run on the string, become distracted, or worse. With time, most dogs that continue in fast cat for the continuous loop system learn to run alongside of the string. 

The Drag Lure System

The other is a drag lure system. The lure is dragged down the middle of the course by a take up wheel powered by a DC motor powered by batteries. The lure stops in the catch pen and needs to be returned to the starting line. Sometimes this has been by hand, sometimes by golf carts or even ATVs. This is better than continuous loop but can be time consuming.  
Fast and Fun developed a return system whereby the lure is attached to a separate trolley that runs along the side of the track. A lure return operator in the catch pen attaches the lure to the trolley, and it is returned to the start. The Huntmaster detaches the lure from the trolley and places it in line for the next run and little if any time is lost. There is no line behind the lure as it travels down the course