Gearbox

The four movements are driven, one at a time, by a two-way radio-control. The most complex part of the mechanism is the one allowing, depending of the positions of the levers (two positions each + neutral, giving a total of 9 combinations), the control of one of the four bidirectional movements (also giving, including neutral, 9 different possibilities).
Each movement is then transmitted, via the trolley and hoisting end-of-course clutches, by worms, the latter giving the reduction ratio required and avoiding the need for brakes.