The Siemens 3SF5402-1AA03 is an AS-Interface F-adapter designed specifically for an EMERGENCY-STOP mushroom-type actuator in the SIRIUS 3SB3 family. It provides two safety-related digital inputs and mounts directly to the front of the panel, not on a DIN rail. The screw-type terminals handle the auxiliary and control circuit wiring.
The two digital inputs are safety-related, meaning this adapter is the interface between the emergency-stop pushbutton and the AS-Interface safety monitor. It does not have any digital outputs — it's purely an input node for the safety circuit.
Front mounting is the specified fastening method — this adapter does not snap onto a DIN rail. It mounts directly behind the panel cutout for the 3SB3 mushroom-head actuator.