Hitachi supplied signalling technology components for safety on China's high speed trains. Hitachi was the supplier to Beijing based Hollyss Automation Technologies Ltd., which is one of the two suppliers along with China Railway Signal & Communication Corp (CRSC) for the signalling equipment. To protect its proprietary technology from competitive threats Hitachi uses zumen or "black box" so that the components cannot be reverse engineered. Experts say that as a result Chinese engineers did not have a good grasp of how crucial aspects of the safety tecnology worked, leading to the collision of two bullet trains in 2011. The key components of the ATP, the Automatic Train Protection, the onboard brain on the trains, was supplied by Hitachi. Engineers at French company Alstom SA's China operations say China needs time to master the complicated technology acquired in the last seven years of the high speed rail program.