The Siemens 5SU9306-1DV40 is a residual current operated circuit breaker with integral overcurrent protection (RCBO) — a combined LS (line/neutral) and DI (fault-current) device in a single 1+N-pole module. The C 40A curve handles motor-start and moderate inrush loads common in commercial distribution boards, while the 30 mA sensitivity covers basic shock protection for socket-outlet circuits. The 6 kA breaking capacity suits domestic and light commercial final subcircuits where the prospective fault current stays under that threshold.
Rated Type AC (CO) — meaning it detects sinusoidal AC residual currents only. For pulsating DC or mixed-frequency faults (common with VFDs, LED drivers, or EV chargers) a Type A or Type F device would be needed instead. The 70 mm depth (D=70mm) is a standard modular dimension that fits flush in most Siemens and compatible distribution boards without protruding past the cover.