The present invention relates generally to a circuit breaker. More particularly, the invention encompasses a modular circuit breaker. The present invention is also directed to a novel a modular circuit breaker with a trip bar. The inventive two pole residential circuit breaker includes an Arc Fault and Ground Fault electronic detection system. The modular breaker design includes an electronic system used for tripping a designated mechanism pole which in turn trips the secondary mechanism pole. Electronic components are included that sense the continuous current flow through each mechanism pole simultaneously to determine when a trip event is needed. The electronic system of this invention includes a self diagnostic system with electronic visual indicators that display the method of which trip condition occurred.