The 5 Main Distribution Board is the central point in an electrical distribution system that receives power from the transformer and distributes it to various sub-circuits within a building. The number of distribution boards in a building depends on its size and complexity. The MDB is the main panel that receives power from the transformer and distributes it to various sub-circuits throughout the building. 5 Main Distribution Board contains the main switch, fuses, and circuit breakers that control the distribution of power.