What is required in the hydraulic jacks of all ATRS systems to ensure functionality?

Check valves are essential components in hydraulic systems, including ATRS (Automatic Train Stop/Train Control) systems, to maintain functionality and safety. Their primary role is to prevent backflow and ensure that the hydraulic fluid remains under pressure when the system is operating. If there were a sudden loss of pressure due to leaks or failures in other components, check valves would help stop fluid from escaping backward, thereby maintaining the necessary pressure needed for the hydraulic jacks to operate effectively. This is critical for ensuring the reliability of the system, particularly in emergency situations.

Other options may play roles in the overall maintenance and operation of hydraulic systems but do not directly contribute to the prevention of sudden pressure drops in the same way. For example, automatic shut-off switches and reservoirs for extra fluid serve different purposes such as enhancing safety and providing adequate hydraulic fluid but do not specifically address the issue of maintaining pressure. Regular monitoring by maintenance personnel is also important for the upkeep of the system but does not directly relate to the immediate functionality of the hydraulic jacks. Therefore, check valves are directly linked to the operational integrity and safety of the ATRS system's hydraulic jacks.