It protects a single-phase outgoing circuit, with the neutral switched on the left side (1P + Ns). The integrated 30 mA earth-leakage protection covers personnel shock hazard and ground-fault detection in one device, saving a DIN-rail slot versus separate MCB and RCCB.
The D-curve means the magnetic trip fires between 10× and 20× In, so a 20 A unit holds through motor-start spikes up to roughly 400 A before instant-tripping. That's the right choice for pumps, compressors, or small conveyors on a lighting panel. The 30 mA earth-leakage sensitivity is the common touch-safe threshold for personnel protection; it also catches deteriorating insulation on motor windings before a hard ground fault develops. The thermal-magnetic trip technology gives you a bimetal element for overload protection and a solenoid for short-circuit — no electronics to fail or drift, which matters in a hot panel or a cabinet near rotating equipment where vibration and temperature swings are the norm. The 20 A rating at 50 °C means it's already derated from the 25 °C reference; you don't lose headroom in a warm enclosure.
Clip-on mounting to a standard 45 mm grid DIN rail. The 18 mm width and 2-pitch spacing mean it occupies two 9 mm positions — standard for a 1P+N RCBO in the Acti9 range. The toggle control provides local ON/OFF indication and the unit is padlockable with a 4 mm hasp for lockout/tagout. Screw-clamp terminals accept up to 25 mm² rigid on the top and 16 mm² on the bottom; torque at 3.5 N.m top, 2 N.m bottom. Strip lengths are 14 mm top, 13 mm bottom.