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

• A. MCB
• B. RCCB
• C. A fuse
• D. RCBO

Answer: (D)

RCBO provides both protections in one unit by combining an RCD (residual current device) with an MCB (miniature circuit breaker). The RCD part watches the balance between live and neutral current; if there’s leakage to earth, it trips to prevent electric shock and fire. The MCB part handles overcurrent, tripping on overload or short circuits to protect wiring from overheating. Putting these together means a single device will disconnect the circuit if there’s either leakage or excessive current.

The other options cover only one aspect each: a fuse or MCB handles overcurrent; an RCCB (RCD) handles leakage only; RCBO is the single unit that does both, hence the best choice.