This article is from the Hanggliding and Paragliding FAQ, by Joao Geada with numerous contributions by others.
It is a powered winch that stays in one spot and which pulls line
in under tension. All of the line on the winch is pulled out, then the
far end of the rope is attached to the glider. On a signal, the winch
pulls the line back in to make the glider climb. When the glider
arrives over the winch, the pilot releases the towline. The tow
tension is a function of the throttle setting of the engine powering