AC/DC Thermal Circuit Breakers The term CIR BRKR THRM refers to a specific type of circuit breaker that can handle both alternating current (AC) and direct current (DC). These devices are designed to interrupt or break an electrical circuit under abnormal conditions, such as excessive current flow, overheating, or other faults. They play a crucial role in ensuring the safety and reliability of electrical systems by protecting against damage from power surges, overloads, or short circuits.