This document provides information about miniature circuit breakers (MCBs). It defines MCBs and describes their main functions of protecting cables from overloads and short circuits. The document discusses the components of an MCB, including the bimetal strip for overload protection and magnetic trip for short circuit protection. It explains multi-9 standard dimensions that allow MCBs to fit into distribution boards. Various MCB ratings, curves, markings and auxiliary components are also outlined.