A circuit breaker is disclosed for an electrical circuit. The circuit breaker includes a tripping unit; at least one current sensor; and an input for a signal, at which a blocking signal for a circuit breaker arranged upstream on the energy sink side, can be received. The tripping unit; at least one current sensor; and an input are all connected to a control unit. A connectable blocking function is provided. The ascertained current is compared with a first current limit value, the exceeding of which requires this first current value to be present for a first period of time in order to prompt interruption of the electrical circuit; and is compared with a second current limit value. Different periods of time need to be present to prompt interruption when the blocking function is disengaged or engaged.