Which device provides both residual current protection and overcurrent protection in one unit?

• A. RCBO
• B. MCB
• C. RCD
• D. RCCB

Answer: (A)

An RCBO provides both residual current protection and overcurrent protection in one unit. It combines an RCD function, which senses an imbalance between live and neutral to detect leakage to earth and trips to prevent electric shocks, with an overcurrent protection function (an integrated MCB) that trips when current is too high due to overload or a short circuit. This means you get protection against shock and protection of the circuit all in one device, simplifying installation and wiring. The other options either protect only against leakage (RCD/RCCB) or only against overcurrent (MCB), so they don’t provide both protections in a single unit.