It's rated 40 A, 3+N-pole, 300 mA sensitivity, 400 V, with a 10 kA breaking capacity at 50 Hz. This is the core earth-leakage protection device for a three-phase panel — catches ground faults on the line side of the load, not the branch circuit.
40 A continuous rating means this RCCB sits upstream of loads drawing up to that current — sized for a sub-distribution board feeding several smaller circuits. The 300 mA residual sensitivity is for fire protection or equipment protection, not personnel shock protection (that's 30 mA or lower). It trips on sinusoidal AC earth faults only (Type AC); if the load has rectifiers, VFDs, or switching supplies that generate pulsed DC fault currents, you'd need Type A or Type B instead.
Deployment context
The 3+N-pole design switches all three phases plus the neutral; the neutral must pass through the device for the residual current sensing to work. Rated 50 Hz only — not suitable for 60 Hz installations or variable-frequency supplies without verifying the core's frequency response.