Bonjour
It is a Navik VR10 .I've never used one.
You may found some information at the end of the Navik Windwane booklet (in French of course) because they used the same hardware to transform the windwane into an autopilot with a small engine that was turning the windvane fletner (starts at p33)
The normal use is to set the desired course on the compas (turning the black button on top). There is an optical system inside the compass that commnd the engine by a left or right order to bring back the boat on course.
The command unit indicates the order status (left, right, nothing) incorporates the on/off button and perhaps a gain setup.
The aerial is mounted in place of the compass and work the same way. You turn the aerial until the vane is in the wind and the wind shifts give correction orders.
Eric