The Schneider Electric A9V31440 is an Acti9 Vigi iC60 add-on residual current device — a 4-pole, 40 A, 30 mA sensitivity block that clips onto the outgoing side of an iC60 MCB to add earth-leakage protection to a final subcircuit. It's Type A-SI (Super Immunised), meaning it handles pulsed DC fault currents and resists nuisance tripping from upstream surge arrestors or switching transients, which is what you want on a mixed-load distribution board with electronic loads. Rated 400 V AC, 50/60 Hz, it mounts on a DIN rail via the clip-on mechanism and occupies 7 x 9 mm pitches (135 mm wide).
Integration is straightforward if you've worked with the Acti9 modular range before. The block screws directly onto the bottom of an iC60 MCB — the tunnel-type terminals accept 1...35 mm² rigid or 1...25 mm² flexible (with or without ferrule), and the tightening torque is 3.5 N·m. The voltage-independent residual current tripping technology means it doesn't draw power from the load circuit to detect a fault — it trips on the leakage current itself, which makes it more reliable on circuits with poor voltage quality.
Standards compliance is solid: IEC 61009-1 and EN 61009-1 for the RCD function, plus IEC 60947-2 for the insulation and impulse withstand (6 kV rated impulse, 500 V insulation voltage). The electromagnetic compatibility rating includes an 8/20 µs impulse withstand of 3000 A per IEC 61009-1, so it survives lightning-induced surges on the line side. The local signalling is a trip indicator — you'll see a mechanical flag in the window when the RCD has tripped, which helps during fault-finding on a multi-circuit board.