The SMC AV4000-F04S-5DZB-A is a soft start-up valve designed to gradually increase initial pressure in an air system and to allow for rapid exhaust by cutting off the air supply. This gradual pressure increase helps prevent the sudden, jerky movements of pneumatic actuators like cylinders, enhancing operational safety and reducing mechanical shock. When the solenoid is de-energized, the valve functions as a 3-port valve, quickly releasing any residual downstream pressure. This model comes complete with a 24VDC solenoid, a built-in silencer for quiet exhaust, and a mounting bracket for easy installation.