The Siemens 5SU9353-7CR40 is a 1P+N residual-current circuit breaker with overcurrent protection (RCBO) from the 5SU9 series. It combines a 40 A C-characteristic MCB with a 30 mA Type A RCD in a single DIN-rail module, rated at 4.5 kA breaking capacity on 230 V AC. The C-curve means it's sized for motor and lighting circuits with moderate inrush — the magnetic trip holds through starting surges up to 5–10× rated current, then clears a hard fault before the cable gets hot.
Snaps onto a standard 35 mm DIN rail in a distribution board. The 1P+N format takes a single module width, so it's a direct fit for compact consumer units or sub-distribution panels where space is tight. Type A RCD detects both sinusoidal AC fault currents and pulsating DC fault currents — that's the right choice for circuits feeding electronics, VFDs, or washing machines where a plain AC type would miss half the fault signature.