Electric circuit breaker, comprising: - a circuit breaker unit including: - at least one electrical conductor (43, 49) equipped with a first fixed pad, - a bridge which is equipped with at least one second pad and is movable between a first position in which the second pad is in contact with the first pad, and a second position in which the second pad is spaced apart from the first pad, - a unit for controlling the movable bridge, - an actuator for the control unit, said actuator being capable of switching between an armed configuration in which it activates the control unit, and a disarmed configuration in which it does not activate the control unit, and - a first electrical coupling module; and - a trip unit including: - an electronic trip circuit, - a second module for electrical coupling with the first coupling module of the circuit breaker unit, the circuit breaker being characterised in that the trip unit is provided with a lock for arming the actuator, said lock being: - resiliently loaded towards a first position in which the actuator is in the disarmed configuration, and - adapted to be pushed back towards a second position in which it switches the actuator into the armed configuration when the first and second coupling modules (58, 64) are electrically connected. - a circuit breaker unit including: - at least one electrical conductor (43, 49) equipped with a first fixed pad, - a bridge which is equipped with at least one second pad and is movable between a first position in which the second pad is in contact with the first pad, and a second position in which the second pad is spaced apart from the first pad, - a unit for controlling the movable bridge, - an actuator for the control unit, said actuator being capable of switching between an armed configuration in which it activates the control unit, and a disarmed configuration in which it does not activate the control unit, and - a first electrical coupling module; and - at least one electrical conductor (43, 49) equipped with a first fixed pad, - a bridge which is equipped with at least one second pad and is movable between a first position in which the second pad is in contact with the first pad, and a second position in which the second pad is spaced apart from the first pad, - a unit for controlling the movable bridge, - an actuator for the control unit, said actuator being capable of switching between an armed configuration in which it activates the control unit, and a disarmed configuration in which it does not activate the control unit, and - a unit for controlling the movable bridge, - an actuator for the control unit, said actuator being capable of switching between an armed configuration in which it activates the control unit, and a disarmed configuration in which it does not activate the control unit, and - a first electrical coupling module; and - a trip unit including: - an electronic trip circuit, - a second module for electrical coupling with the first coupling module of the circuit breaker unit, the circuit breaker being characterised in that the trip unit is provided with a lock for arming the actuator, said lock being: - resiliently loaded towards a first position in which the actuator is in the disarmed configuration, and - adapted to be pushed back towards a second position in which it switches the actuator into the armed configuration when the first and second coupling modules (58, 64) are electrically connected. - an electronic trip circuit, - a second module for electrical coupling with the first coupling module of the circuit breaker unit, - resiliently loaded towards a first position in which the actuator is in the disarmed configuration, and - adapted to be pushed back towards a second position in which it switches the actuator into the armed configuration when the first and second coupling modules (58, 64) are electrically connected.