The Siemens 5SU9306-1KK45 is a SENTRON RCD-operated circuit breaker — an RCBO that combines overcurrent protection and residual current detection in a single 18 mm wide module. The 1P+N configuration protects one phase conductor while switching the neutral, and the unit occupies a single width unit on the DIN rail.
The 45 A rating is the current at 30 °C; at 40 °C ambient it derates to 42.3 A, at 45 °C to 40.95 A, and at 55 °C to 36.45 A.
The supply can enter from either the top or bottom — no mandatory orientation. Touch protection is built in.