___________ port speed control affects the speed of an actuator in both directions.

The concept of port speed control that affects the speed of an actuator in both directions refers to how the flow of air is managed as it enters and exits the actuator. The correct answer highlights the significance of pressure as a critical factor in controlling the speed of the actuator.

When pressure is adjusted in pneumatic systems, it directly influences the flow rate of the compressed air entering and exiting the actuator. By regulating the pressure, the speed at which the actuator extends or retracts can be effectively controlled, allowing for the same control in both directions of movement. This control is vital for applications where balanced and precise actuator movements are necessary.

In contrast, other options may pertain to specific functions but do not encapsulate the comprehensive control of an actuator across both operational directions in the same way that adjusting pressure does. Understanding how pressure impacts flow rates and actuator speeds forms the foundation of effective pneumatic system design and operation.