The SMC AV4000-04-5DZB is a soft start-up valve designed to gradually increase pressure in a pneumatic system for safer machine operation. It prevents the sudden, uncontrolled movement of actuators like cylinders upon startup by slowly raising the air pressure to the set point. When the power to the solenoid is turned off, the valve rapidly exhausts the downstream air. This 3-port valve is part of SMC’s modular air preparation (FRL) family, allowing for easy integration and space-saving installation. It is an essential safety component for complying with machine safety standards by providing a reliable method for air supply and exhaust.