Do you have a context to this question?
Is it part of the Citroen, or something you've seen somewhere else?
It's labelled fuse in the box, it's shared with the instrument cluster.
I assume it's to allow the fitment of something re. use as a driving school car. Just struck as little odd that the car was specifically designed for it.
Brakes wise the Fabia is sounding very like the C3 prior it's recent 4 disc and pad change. The rears especially were horrific, they weren't straight when you pressed the pedal for a harder stop you could feel it stopping unevenly as it started to lean on the rears more. When you brake gently the fronts are doing most of it.
As it was on that the discs were so bad that although there was pad material left you'd have destroyed the nice new discs leaving it.