The Schneider Electric A9F06240 is a 40 A, 2-pole miniature circuit breaker from the Acti9 iC60H range, with a B-curve trip characteristic. The B-curve means the magnetic trip fires at 4 x In (±20%) — so for this 40 A breaker, instantaneous trip occurs between roughly 128 A and 192 A. That's a good fit for resistive or general-purpose loads where you don't want nuisance trips from moderate inrush.
Breaking capacity and where it matters
This breaker's interrupting capacity is 42 kA Icu at 12–133 V AC, 30 kA at 220–240 V, 15 kA at 380–415 V, and 10 kA at 440 V AC (per EN/IEC 60947-2). Under the 60898-1 standard it's rated 15 kA Icn at 400 V. That's a high-fault-rated device — it can handle the fault currents you'd see close to a transformer or in a heavy industrial panel, not just a light commercial sub-board. The 2-pole version protects both phase and neutral on a single-phase circuit, or two poles of a three-phase system.
Snaps onto a DIN rail — 36 mm wide (4 x 9 mm pitches), 91 mm tall, 78.5 mm deep. That's a standard 2-module width for a 2-pole MCB in the Acti9 family, so it fits existing DIN-rail enclosures and distribution boards without surprises. The double-terminal design (top and bottom) lets you daisy-chain outgoing circuits without piggybacking on the busbar.