In BF3, how does Reactive Armor work?

There are three panels, protecting the sides and rear of the tank. No protection is given to the front of the tank. Each one can take one incoming rocket, tank shell or AT Mine before being destroyed. Once the tank's health has been repaired, the panels can be repaired by a friendly engineer. Enemy engineers can't destroy the armour using a repair tool but they can by using their RPG/SMAW or AT MINE.

To repair the Reactive armour the tank must be at 100% health. If you do know what parts of the tank does not have the armour, use the repair tool and repair the side for 3-5 seconds and should be back up.