Abstract: The present invention relates to a circuit breaker (20, 40) comprising a handle (33) connected to a switching and trip mechanism (25) in the base unit (20a), and capable of opening and closing a system (24) of electrical contacts in normal operation, ensuring the interchangeability between a pluggable electronic trip module (20b) and/or a pluggable thermomagnetic trip module (20b), using the same structural base unit (20a). The device comprises a main electric circuit “1” and a secondary circuit “2” or “2b”, wherein the main circuit “1”, using a current transformer (29) in the base unit (20a) which converts a current flowing in the main circuit “1” of the power line (23) to power the secondary circuit “2” or “2b”, issues a trip command to protect the main circuit “1”, opening the contact system (24) when predefined current limits are exceeded.