The Siemens 5SU1656-6KV20 is a combined residual-current device and miniature circuit breaker (RCBO) — an FI/LS-protector Type A (PSE/SSF) — in a single 1+N-pole unit. It integrates overcurrent protection (B-curve, 20A) with a 300mA residual-current trip, rated for a 6kA short-circuit capacity. The 'Type A' designation means it detects pulsating DC fault currents in addition to sinusoidal AC, making it suitable for circuits with single-phase electronics like washing machines, heat pumps, or EV chargers where simple AC-only RCDs could be blinded. The 300mA sensitivity is a delayed-trip (S-type equivalent) often used for fire protection or circuits where nuisance tripping from leakage currents in long cable runs would be a problem. The 70mm depth (D=70MM) fits standard Siemens distribution boards and most DIN-rail enclosures.
For a sourcing buyer, the 'current' status means the part is available through standard Siemens distribution channels. If you are filling a BOM line or stocking spares, this part is a safe, non-obsolete pick.
Where this class of device is used
FI/LS-protectors (RCBOs) like this one are installed in final distribution boards to protect individual circuits. They combine overcurrent and earth-fault protection in one DIN-rail module, saving panel space compared to a separate MCB and RCD. The Type A characteristic plus 300mA sensitivity makes this a common choice for commercial kitchens, laundries, and any circuit feeding single-phase inverter-driven loads where a standard Type AC RCD would be at risk of failing to trip on a pulsating DC fault.