The Siemens 3SF5811-2AB08 is an AS-Interface emergency-stop slave — a safety-rated E-STOP pushbutton with integrated AS-i communication. It is designed for floor-mounting in industrial control panels or machines where a hardwired emergency-stop function needs to report its status over the AS-i bus. The actuating element is a red mushroom pushbutton with a rotate-to-unlatch mechanism, meaning the operator must twist the button to release it after a stop. Positive opening is confirmed, so the NC contacts are mechanically forced open when the button is pressed — no spring reliance.
Rated for 30 V DC on the AS-i bus, which is standard for AS-Interface systems. The slave type is F slave, 2I — this is a safety slave with two inputs, typically used to monitor the E-stop contacts and any additional feedback (e.g., contactor auxiliary). IP67 protection class means the enclosure and pushbutton are sealed against dust ingress and temporary immersion — suited for washdown environments, food processing, or outdoor installations where hose-down cleaning is routine. The 22 mm mounting diameter fits standard industrial control panel cutouts. The square metal enclosure (85 x 85 x 114 mm) provides rugged mechanical protection and is fastened vertically or horizontally.