Where it goes in the panel
The 5SY4514-8CV: Snaps onto standard DIN rail inside a distribution board or control enclosure. The 1P+N configuration switches the phase and provides a switched neutral — common in single-phase final subcircuits where you need to isolate both conductors. The D0.3 rating is unusual: 0.3 A is a low current for an MCB, so this is likely protecting a control transformer primary, a signaling circuit, or a small power supply, not a general lighting or socket outlet circuit.