The Schneider Electric A9N21377 is a Prodis DT40N miniature circuit breaker (MCB) rated at 20 A with a D tripping curve, meaning the magnetic trip operates at 10 to 14 times the rated current (10...14 x In). Neutral position is left. Clips onto a DIN rail with toggle control and ON/OFF indication. Breaking capacity is rated at 6 kA Icn per EN/IEC 60898-1 for domestic-type installations, and 10 kA Icu at 230...240 V AC per IEC 60947-2 for industrial panel applications.
Clip-on mounting to DIN rail (35 mm) with a 2-pitch width (9 mm per pitch = 18 mm total). The compact 18 mm width per pole saves rail space in crowded enclosures.
Certified to both EN/IEC 60898-1 (household-type MCB standard) and EN/IEC 60947-2 (industrial circuit-breaker standard). This dual certification is the key compliance advantage — it covers residential, commercial, and light industrial installations under one part number. Overvoltage category IV (for equipment connected at the origin of the installation, before the main distribution board). Earth-leakage protection requires a separate block (not integrated).