The main parts are the Miniature Circuit Breaker (MCB), Residual Current Device (RCD), busbars, and the main switch. Safe habits and checking the box often help stop electrical accidents. These are MCBs, RCDs, busbars, and the. For procurement professionals, electrical contractors, and project managers, choosing the right Distribution Box (DB Box) is a critical decision that directly impacts system safety, reliability, and long-term operating costs. This ultimate guide explains what a distribution box does, its internal. Wiring diagram shows both PNP and NPN wiring. Actual units use PNP status indicator, NPN status indicator, or neither. Dimensions are shown in mm (in.