What controls hydraulic valves in elevator systems?

Hydraulic valves in elevator systems are specifically controlled by hydraulic valve control mechanisms. These controls are designed to manage the flow of hydraulic fluid that moves through the valve, allowing for precise operation of the elevator's movement and stopping capabilities.

Hydraulic valve control mechanisms utilize various components, such as solenoids or manual levers, to regulate the direction and speed of the hydraulic fluid. This is crucial for ensuring that the elevator operates smoothly and safely, as it allows the control system to manipulate the pressure applied to the hydraulic cylinders responsible for lifting and lowering the elevator car.

The other options do not directly control the hydraulic valves in the way that hydraulic valve control does. For example, pneumatic actuators operate using compressed air, which is unrelated to hydraulic systems that rely on fluid. Hydraulic pressure, while essential for the operation of the elevator, is the result of the actions taken by the hydraulic valve control rather than a controlling mechanism itself. Mechanical linkages can be used in some systems, but they do not specifically manage hydraulic valve operations in the context of where hydraulic pressure is used for elevating systems. Therefore, the understanding that hydraulic valve control directly influences the functioning of hydraulic valves in elevator systems is imperative for the effective operation of these systems.