All present-day Vane Steering gears use the same operating principles.
A windvane reacts to changes in the apparent wind direction and transmits this reaction to the servo pendulum in the water which, in turn, operates the boat’s steering or an auxiliary rudder.
The windvane itself does not possess sufficient power to steer the boat, this is augmented by the servo pendulum. The energy required for this is generated by the forward motion of the boat, through the flow of the water along the submerged portion of the servo pendulum. The connection between the wind-vane and the servo pendulum is through struts or a gear train.