The G12E4F40 is a Schneider Electric GoPact MCCB 125 — a 4-pole moulded-case circuit breaker with a TM-D thermal-magnetic trip unit rated at 40 A at 40 °C. The TM-D gives you L (thermal overload) and I (magnetic short-circuit) protection in one block, so it handles distribution feeder duty without a separate relay. The 440 V rated insulation voltage and overvoltage category III mean it's built for fixed-installation mains supply, not downstream equipment. The IP20 finger-safe enclosure is standard for panel-mount; you don't need to seal it for a dry indoor cabinet.
Mounting and integration — backplate fixed, front connections
Mounts fixed to a backplate — no DIN-rail clip here, so plan for screw-down lugs or a dedicated mounting bracket in the enclosure. Both line and load connections are on the front, screw terminals with a 25 mm connection pitch. The neutral sits on the left and the 4D protected poles cover all four poles with neutral protection set at 1 x Ir. The 100 x 130 x 60 mm footprint is compact for a 4-pole 40 A breaker; watch the 18.7 W power dissipation per pole if you're stacking multiple units in a sealed enclosure — derate or add ventilation above 40 °C.