Abstract: A circuit breaker suitable for use on both AC and DC circuits includes a magnetically permeable core surrounding a current carrying conductor of the circuit breaker. A bimetal member is thermally coupled to the core such that induction heating of the core due to overload AC current flowing through the conductor is operative to deflect the bimetal and actuate a trip device. The circuit breaker also includes a pair of braided copper shunts connected between the conductor and the bimetal such that resistive heating of the conductor due to overload DC current flow through the breaker will cause the bimetal to deflect and actuate a trip device. The bimetal is mechanically isolated from the conductor such that relative movement therebetween will not affect thermal calibration of the circuit breaker.