This Hitachi catalog presents Miniature Circuit Breakers (MCBs) and Residual Current Circuit Breakers (RCCBs) for comprehensive electrical circuit protection. The MCBs (BK63 & BTK63 series) provide overload and short-circuit protection for household and commercial installations, featuring rated voltages of 230/400V or 240/415V AC, 50/60Hz frequency, and rated currents up to 63A. They offer B, C, and D tripping characteristics (3-5In, 5-10In, 10-20In respectively) suitable for diverse applications from electronic equipment to heavy-load motors, with breaking capacities of 6kA (BK63) or 10kA (BTK63) and thermal magnetic release. The RCCBs (RK63 series) offer indirect protection against electric shock and fire hazards caused by earth fault currents, operating at 240/415V AC with rated currents up to 63A and non-adjustable residual current sensitivities of 30, 100, or 300mA, tripping within ≤0.1 seconds via electro-magnetic release. Both product lines are designed for 35mm DIN rail installation, comply with IEC standards (IEC60898 for MCB, IEC61008 for RCCB), and boast electrical endurance of 6,000 to 8,000 operations.