Circuit breakers are switching devices capable of making, carrying and breaking currents under normal circuit conditions and making, carrying for a specified time, and breaking current under specified abnormal conditions such as a short circuit. Low voltage circuit breakers have voltage ratings from 250 to 600 V AC and 250 to 700 V DC. The molded case circuit breaker is one of the two basic low voltage classes of circuit breakers. The other class is the low voltage power circuit breaker. Medium voltage circuit breakers are rated up to 72.5 kV. ANSI or IEC is normally the governing standard for medium voltage circuit power breakers. ANSI is associated with U.S. standards, and IEC is associated with international standards. For standard definitions, refer to ANSI 37.100 Definitions for Power Switchgear.