AS-Interface Emergency-Stop with Positive-Opening Contacts
The Siemens 3SF5811-2AA08 is a self-contained emergency-stop pushbutton designed for AS-Interface safety networks. It integrates an EMERGENCY-STOP mushroom pushbutton (red actuator, yellow enclosure top) with an AS-Interface F slave (type 2I), meaning it reports two input channels directly onto the AS-i bus without a separate I/O module. The positive-opening contacts (IEC 60947-5-1, clause K.2.1) mechanically force the normally-closed circuit open even if the contacts weld — this is the core safety feature for a category 0 or 1 stop per EN ISO 13850. The rotate-to-unlatch mechanism prevents accidental reset; the operator must twist the actuator to release it, which is the standard for guarded equipment restart.
IP67 Sealing and Metal Enclosure for Washdown Environments
Rated IP67, the 3SF5811-2AA08 withstands temporary immersion and hose-directed water — suitable for food-processing lines, washdown stations, or outdoor conveyor transfer points where moisture and debris are present. The metal enclosure (holder and housing) provides impact resistance in high-traffic areas where plastic could crack. The 22 mm round mounting hole is the standard industrial pilot-device cutout, so it retrofits into existing panel punches without adapter plates. Vertical fastening method is specified; the square front profile (85 mm × 85 mm) occupies a standard footprint on the enclosure surface.
AS-Interface F Slave with Pre-Wired Termination
The 3SF5811-2AA08 is an AS-Interface F slave (fail-safe slave) with two digital inputs (2I), meaning it directly connects to an AS-i safety monitor without an intermediate safety relay. The F-slave designation per AS-Interface Safety at Work (IEC 62061) supports SIL 3 / PL e architectures when paired with a compatible safety monitor. The unit ships pre-wired on a strip terminal, which simplifies field installation: no need to open the enclosure for wiring — just terminate the AS-i flat cable and the strip connector. The DC operating voltage is supplied directly from the AS-i bus (30 V DC nominal per the AS-i specification), so no separate power supply is needed for the slave electronics.