The Siemens 5SU1656-7KV20 is an FI/LS-protector (RCBO) combining Type A residual current protection at 300 mA sensitivity with a C-curve 20 A overcurrent trip in a single 1+N-pole module.
The Type A residual current detection handles pulsating DC fault currents from rectified loads — modern electronics, LED drivers, and variable-speed drives — which a standard Type AC would miss. At 300 mA sensitivity it is sized for fire protection rather than personnel protection (30 mA), so it is appropriate for fixed equipment circuits where the earth leakage from normal operation is too high for a 30 mA device.