MOST Fibre optic interface to allow the fitting of a new head unit into a Landrover  Freelander , Discovery3, Range Rover Sport, Range Rover Vogue with the Premium sound original audio and retain the use of the fibre optic amplifier.
You will lose front to rear fading ability.

if the car has speaker wiring in the  audio connector  then it is NOT a fibre-optic amplified system and this interface is not needed.

 This interface does not retain the use of the steering wheel controls.You should use separate steering control interfaces