The Schneider Electric A9F03706 is a 3P+N miniature circuit breaker from the Acti9 iC60 range, rated at 6 A with a B-curve tripping characteristic. It's a thermal-magnetic MCB for distribution boards, certified to both EN/IEC 60898-1 and EN/IEC 60947-2, so it covers residential and industrial coordination requirements. The 36 kA Icu at 12–133 V AC gives you serious fault-clearing headroom on the low-voltage side of a transformer—useful when the service entrance feeds a sub-distribution board with high prospective fault current.
Breaking capacity drops with voltage: 36 kA Icu at 12–133 V AC, 20 kA at 220–240 V, 10 kA at 380–415 V, and 6 kA at 440 V. The Icn rating under EN/IEC 60898-1 is 6000 A at 400 V AC. For a 6 A MCB, that's more than enough for most final circuits, but the 10 kA at 400 V matters if you're coordinating with an upstream device in a panel with limited through-fault energy.
Snaps onto a DIN rail, 72 mm wide (8 x 9 mm pitches), 91 mm tall, 78.5 mm deep. IP20 finger-safe front. Double terminals top and bottom accept 1–25 mm² rigid or 1–16 mm² flexible; strip 14 mm, torque to 2 N.m. Neutral is on the left, fixed position. The toggle switch gives a clear trip-indicator flag—no guessing whether it's off or tripped.