Miniature Circuit Breaker (MCB): These are automatic electrical switches that are designed to protect electrical circuits from damage caused by overload or short circuit. They are commonly used in domestic, commercial, and industrial electrical installations to provide protection to individual circuits.

Distribution Board (DB): Also known as a breaker panel or electric panel, a distribution board is a component of an electrical supply system that divides an electrical power feed into subsidiary circuits while providing a protective fuse or circuit breaker for each circuit.

Double Door (DD): This likely refers to the design of the distribution board. Double-door distribution boards typically have an outer and inner door. The outer door provides protection from the elements and unauthorized access, while the inner door provides access to the circuit breakers or fuses inside.

4-Way: This indicates that the distribution board has four circuits or ways. Each circuit typically corresponds to a different area or type of electrical load.