The 5SM1614-6FD is a Siemens FI-PROTECTOR Type A residual current device (RCD) in the PSE/SSF form factor. It's rated 40A, 2-pole, with a 0.3A rated residual operating current (IΔn) at 230V, and occupies 2TE (36mm) on a DIN rail. The 55mm depth fits standard distribution boards.
Type A detection means it responds to AC residual currents and pulsed DC residual currents up to 6mA — the standard for circuits with single-phase rectifiers, switched-mode power supplies, or variable-speed drives. The 0.3A IΔn is a common threshold for general-purpose protection in commercial and industrial sub-distribution; it's not the 30mA required for personal shock protection in final circuits. At 40A it's sized for a main incoming or sub-main feeder, not a branch circuit. The 2-pole construction (L + N) is correct for single-phase 230V systems.