The Siemens 5SJ6405-7 is a 4-pole miniature circuit breaker from the SENTRON 5SJ6 series, rated 0.5 A with a C tripping characteristic. It protects branch circuits against overloads and short circuits, with a breaking capacity of 6 kA per both EN 60898 and IEC 60947-2 — enough for most residential and light commercial distribution boards where the prospective fault current stays under that threshold.
Rated 0.5 A at 400 V AC, this breaker is sized for very light loads — think control transformers, signal supplies, or small lighting circuits, not motor or general-power branches. The 6 kA breaking capacity (per EN 60898 and IEC 60947-2) is the standard domestic/commercial rating — it will clear a fault up to 6 kA without welding or rupturing. Four poles mean it switches all phases (and the neutral if wired that way) simultaneously. The 4-module width (each 18 mm, so 72 mm total) is the standard footprint for a 4-pole MCB on a DIN rail — it occupies four adjacent slots in the distribution board.
Installation depth is 70 mm — that's the distance from the rail to the back of the enclosure, so the panel needs at least that much clearance behind the rail. Rated for 50 Hz supply, overvoltage category III (fixed-installation level), and sealable (provision for a lead seal or lock to prevent unauthorized switching).