The Siemens 5SY4105-8CV is a 1-pole miniature circuit breaker (MCB) from the 5SY4 series, rated D0.5 with an ultimate breaking capacity (Icu) of 15 kA at both 230 V and 400 V AC. The 0.5 A rating is a fine protection level for low-current control circuits, instrumentation loops, or PLC digital input power feeds.
In a 400 V three-phase panel with a transformer-fed supply capable of 10 kA fault current, this breaker provides adequate interrupting margin. No auxiliary contact or shunt trip is integrated in this base variant; those are separate add-on modules that clip onto the right side of the breaker.