The A9N4P20DGN is a 4-pole miniature circuit breaker from the Schneider Acti9 xC60 range, rated 20 A with a D tripping curve. The 10 kA Icn breaking capacity at both 240 V and 415 V AC (50/60 Hz) meets the IS/IEC 60898-1 standard for residential and light commercial distribution boards, so it safely clears a fault up to that level without welding the contacts or cascading upstream. Thermal-magnetic trip technology gives it the dual response: a bimetal strip for overload protection (time-delayed) and a solenoid for short-circuit protection (instantaneous above the magnetic threshold). The 4-pole configuration (4P) switches all phases and the neutral simultaneously, which is standard for three-phase distribution where you want the neutral isolated when the breaker is off.
At 72 mm wide (8 x 9 mm pitches) and 85 mm tall, it occupies four modular spaces in a distribution board. Depth is 77.5 mm, which fits most consumer units and sub-distribution enclosures; verify the gland plate depth if the enclosure is shallow. Wire stripping length is 13 mm for both top and bottom connections.
Overvoltage category IV means it's rated for installation at the origin of the installation (utility side of the main distribution board), not just downstream sub-circuits. IP20 finger-safe on the front; the busbar area is live when the breaker is on, so the enclosure door should be lockable or tool-accessible. Electrical and mechanical durability are both rated at 20,000 cycles, which is standard for a distribution MCB; expect the mechanical life to exceed the electrical if it's used mainly as a disconnect rather than a daily switch.