The Schneider Electric A9KF71204BQ is a 2-pole miniature circuit-breaker from the Acti9 K60 series, rated 4 A with a C-curve trip characteristic.
The C-curve (magnetic trip 5 to 10 x In) means this breaker is designed for moderate inrush loads — typical for lighting circuits, small transformers, and general-purpose socket outlets. It will hold through the brief start-up surge of a small motor or a bank of fluorescent ballasts, but trips fast on a hard short. The 4 A rating and 2-pole configuration protect a single-phase 230 V line-and-neutral circuit drawing up to 4 A continuous. Thermal-magnetic trip technology gives two-stage protection: a thermal bimetal for overloads (slow, inverse-time) and a solenoid for short-circuits (instantaneous). No earth-leakage protection is built in — that is handled by a separate RCCB upstream if required.
The 81 mm height and 70 mm depth fit standard distribution board enclosures. IP20 rated for dry indoor panels; pollution degree 2 means it is suitable for normal non-conductive contamination environments. This covers most final-circuit cable sizes up to 4 mm² comfortably, with headroom for paralleled feeds.