A circuit breaker for controlling a power supply to electrical appliances connected to a power line. The circuit breaker comprises: a signal acquisition module configured to acquire an electrical power signal indicative of the power supply; a circuit breaker mechanism configured to selectively interrupt the power supply to the one or more electrical appliances based on the electrical power signal; an event detection module configured to detect an event associated with operation of one or more of the electrical appliances based on electro-magnetic interference (EMI) generated by the event; and a feedback module configured to control one or more feedback actions in dependence on the detected event. The event detection module is configured to: identify one or more EMI features in the electrical power signal; compare the one or more identified EMI features to an event database comprising event records, and detect the event based on the comparison.