DIRAVI is an acronym for "Direction à rappel asservi" literally meaning "steering with controlled return" more accurately described in English as "power steering with power assisted return".
When the gears are turned relative to each other, the rods move the slide valve, allowing fluid in or out of the rack.
Compare this with a conventional power steering system, which relies on the flexing of a strong spring to control the valve.
As with a normal power-assisted steering setup, there is a rack-and-pinion, and a stepped hydraulic ram with a dividing plate (the piston) in the middle.
Thus, with full system pressure on the small area side of the ram, and half system pressure on the large area side, the ram remains perfectly balanced and centred.
Enough pressure was admitted to the centring unit to return the wheels to the straight ahead position when the car was not moving.
When there is no pressure available to operate the ram, the steering wheel will mechanically move the rack directly but with significant play through a split shaft.
[6] One side from the steering wheel drives a pin which mates with a slot on the output shaft connected to the rack.