The Siemens 5SU1156-0KV13 is a combined residual-current device and miniature circuit breaker (RCBO) — often called an FI/LS protector in European panel practice. It packs Type AC earth-leakage detection and overcurrent protection into a single 1+N-pole unit, saving a DIN-rail slot compared to separate RCD and MCB. The 10 mA IΔN (rated residual operating current) is the sensitive end of the Type AC range — it trips on sinusoidal AC fault currents down to that threshold. That makes it a fit for circuits where a higher 30 mA trip would leave a hazardous touch-voltage exposure, like lighting circuits in wet areas or certain medical locations. The B-curve 13 A thermal-magnetic characteristic means the magnetic trip operates at 3 to 5 times rated current (39–65 A), so it clears fast on a hard short but tolerates the inrush of resistive and modestly inductive loads like lighting banks or small control transformers. It's not sized for motor-starting surges — those need a C or D curve.
Where it goes in the panel
The 70 mm width (4 module spaces) clips onto standard DIN rail. The 1+N-pole configuration switches and protects the phase conductor only; the neutral is switched through the RCD element but not overcurrent-protected.