The A9F08204 is a 4 A, D-curve, 2-pole miniature circuit breaker from the Schneider Electric Acti9 iC60H series. It's a thermal-magnetic MCB rated for distribution circuits, and the D curve means its magnetic trip threshold is 12 x In (48 A), so it handles the inrush of small motors and transformers without nuisance tripping — that's the key fit decision for this part. Breaking capacity is 70 kA Icu at 220-240 V AC and 380-415 V AC per EN/IEC 60947-2, and 10 kA Icn at 400 V per EN/IEC 60898-1. It's certified to both EN/IEC 60947-2 (industrial) and EN/IEC 60898-1 (domestic), so it qualifies for either duty. The 2-pole configuration protects both phase and neutral, and the IP20 finger-safe terminals keep the panel builder out of trouble during commissioning.
It's 36 mm wide (4 x 9 mm pitches), 91 mm tall, and 78.5 mm deep — that 78.5 mm depth matters when you're laying out a gland plate or a shallow enclosure; it leaves room for wiring behind the breaker. Terminals accept 1-25 mm² rigid or 1-16 mm² flexible wire, double-terminal top and bottom. That double terminal lets you daisy-chain the feed without a separate distribution block — saves a DIN position.
The tropicalisation rating (2 per IEC 60068-1) and pollution degree 3 rating mean it's suited for humid or dusty environments — not just a clean control room.