Wikipedia
DIRAVI is the name given by Citroën to its proprietary power steering system, first seen in 1970.
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". In the UK, it was marketed as VariPower and in the U.S. as SpeedFeel.
This was the first commercially available variable assist power steering arrangement, allowing the motorist power assist when parking, but recognizing that less steering assistance was needed at high speed. This feature is now spreading to mainstream vehicles, using electrical motors rather than hydraulic actuation.
Citroën engineer Paul Magès invented the system as part of its effort to engineer a practical high horsepower, front wheel drive car - a new type of vehicle at the time.
This DIRAVI system is an addition to the integrated Citroën hydropneumatic suspension and braking system. These all drew power from an engine driven pump and hydraulic accumulator.
This unique Citroën power operated self centring steering system is fitted to: Citroën SM, Citroën CX (most), Citroën XM (early Left Hand drive V6), Maserati Quattroporte II, Maserati Khamsin