The solenoid valve supplying air to that actuator must have four ports: one for air supply (P), one for exhaust (E), and two for the cylinder ports (typically labeled A and B), so that to make a pneumatic actuator move two different directions. These valves are required for double-acting cylinders because they actually switch the direction of airflow from going in the bottom of the cylinder inlet to going Nan tèt lòt pò silenn lan . sa a ede silenn lan louvri epi fèmen trè rapidman . sa a ki kalite valv se pi plis itil lè diferan kalite likid ke yo te melanje youn ak lòt nan yon sèten rapò fiks .
