The Schneider Electric A9D51225 is an Acti9 iC60 RCBO — a combined residual-current circuit breaker with overcurrent protection in a 2-pole, 25 A, C-curve variant. It integrates earth-leakage detection at 300 mA sensitivity and thermal-magnetic overcurrent protection into one 36 mm wide DIN-rail module, saving a panel position versus separate devices.
Rated 25 A at 50 °C with a C-curve trip characteristic — magnetic release between 5 and 10× In, so it handles motor inrush and lighting ballast surges without nuisance tripping, but still clears a hard short fast. The 10 kA Icn breaking capacity at 240 V AC is the maximum fault current the device can safely interrupt; for most commercial and light industrial distribution boards on a 240 V single-phase supply this is adequate, but verify the prospective short-circuit current at the point of installation. The 300 mA earth-leakage threshold is a protection level for fire prevention or equipment protection, not personnel shock protection (that would be 30 mA or lower). Tightening torque is 3.5 N·m top, 2 N·m bottom.