Folding traction current collection device mounted on the roof of a vehicle on a railway employing an overhead supply system. Nowadays, pantographs are sophisticated aero-dynamically designed devices which can operate at high speeds without loss of contact and with built-in safety devices which reduce the risk of damage to wires in the event of a fault. A common problem is when a pantograph catches above the wire and pulls it down for considerable distances before it is noticed by the crew and the train stopped. Modern pantographs are fitted with automatic detection and lowering devices. The horns (curved edges) of the pantograph are equipped with frangible pneumatic sensors which, if broken by a wire support, cause the detector system to lower the pantograph.