This third razor wire barrier cost Spain €33 million to construct. It consists of of parallel high fences topped with barbed wire, with regular watchposts and a road running between them to accommodate either police patrols or ambulance service in case of need. Underground cables connect spotlights, noise and movement sensors, and video cameras to a central control booth. In 2005 its height was doubled to since immigrants were climbing the previous fences equipped with home-made steps. Also, in order to facilitate the intruders' detention, devices to slow them harmlessly were added.