 Reversing was achieved by a simple sliding camshaft system.Many locomotives in France, particularly those rebuilt to the designs of Andre Chapelon, such as the SNCF 240P, used Lentz oscillating-cam poppet valves, which were operated by the Walschaert valve gear the locomotives were already equipped with.The poppet valve was also used on the American Pennsylvania Railroad's T1 duplex locomotives, although the valves commonly failed because the locomotives were commonly operated in excess of , and the valves were not meant for the stresses of such speeds.