The Siemens 5SU1654-7RC40 is a 40 A, 2-pole RCBO in a 2-module width, combining overcurrent protection with a Type A residual-current device rated at 300 mA. Type A sensitivity detects pulsating DC fault currents, covering electronics and single-phase rectifier loads that a plain AC type would miss.
The 2-module (36 mm) width snaps onto DIN rail in a standard distribution board. Two poles switch both line and neutral; the outgoing terminals accept copper conductors up to 25 mm². Panel builders should account for the 300 mA residual-current threshold when coordinating downstream RCDs — this is a higher threshold than a 30 mA unit, intended for equipment protection rather than personal shock protection.