Here, a double pole MCB is used as the Main MCB or Main switch. The single input supply (phase and neutral) is connected to this main MCB. A distribution box is a low-voltage electrical enclosure that receives incoming power and distributes it safely to multiple outgoing circuits through protective and switching devices such as MCBs, RCDs, RCBOs, fuses, isolators, busbars, neutral bars, earth bars, and surge protective devices. The. A distribution box is a key part of electrical systems in buildings. Inside, you'll find parts like circuit breakers and fuses that protect the system from problems like overloads and short circuits.