Describe the function of a 4/2 pneumatic valve in a simple actuator circuit.

• A. It controls the extend/retract of a cylinder by directing compressed air to the appropriate ports and exhausting the opposite port
• B. It reduces air pressure to a adjustable level
• C. It filters the air entering the system
• D. It measures cylinder position

Answer: (A)

A 4/2 valve acts as a directional control switch that decides which end of a double-acting cylinder gets pressurized air and which end is vented. In a simple actuator circuit, this directs extend versus retract: in one position, the valve routes compressed air to one cylinder port while exhausting the opposite port; in the other position, the supply is swapped so the other side is pressurized and the first is vented. This is why it controls movement rather than reducing pressure, filtering air, or measuring position.