The 5SM3444-0LB: The 40 A rated current and 100 mA residual sensitivity suit general-purpose AC circuits where earth-leakage protection is required — typical for sub-distribution boards feeding socket outlets or fixed equipment. The 4-pole construction (3 phases + neutral) matches a three-phase supply with switched neutral, common in European-style TN or TT systems.
Mounts on DIN rail (REG) in any position, occupies 4 width units (about 72 mm). Terminals accept solid or stranded conductors from 1.5 to 25 mm²; tighten to 2.5–3 N·m. Overvoltage category III, finger-and-back-of-hand safe per the design.