In which type of valve are the system and circuit relief valves typically found?

System and circuit relief valves are typically associated with directional control valves, making this the correct choice. Directional control valves are crucial in hydraulic and pneumatic systems as they control the path of fluid flow and can manage various system functions, including relieving pressure.

In hydraulic systems, the relief valve is an integral safety component that prevents excessive pressure buildup, which can damage the system components. It achieves this by allowing fluid to flow back to the reservoir or return line when the pressure exceeds a designated threshold.

While pressure regulating valves maintain consistent pressure levels, they are not specifically designed to serve as relief valves. Check valves, on the other hand, allow fluid flow in one direction only and do not have any feedback control mechanisms. Flow control valves are primarily used to regulate the flow rate of the fluid, not to manage system pressure. Thus, relief valves are most commonly found in the context of directional control valves, underscoring their critical role in ensuring proper operation and safety within hydraulic systems.