The Siemens 5SU1654-7KV20 is a combined residual-current device and miniature circuit breaker (RCBO) — an FI/LS protector in Siemens' terminology. It integrates Type A residual current detection at 300 mA with a 1+N-pole thermal-magnetic overcurrent trip characteristic C rated at 20 A, all in a 70 mm wide housing. The 10 kA breaking capacity means this unit can safely interrupt fault currents up to that level at the rated voltage, which is the standard for final subcircuits in commercial and industrial distribution boards where the prospective short-circuit current is known to stay under that threshold.
The 70 mm module width (4 TE on a standard DIN rail) occupies four 18 mm pitch units in the distribution board. Plan for this when laying out multi-pole RCBO combinations in a crowded enclosure — the 1+N-pole format saves one module width versus a 2-pole device for the same single-phase protection scheme.