A circuit breaker includes a bimetallic snap-action disk fixed to a bimetallic connection disposed in the vicinity of a fixed contact connection inside a coverable housing. The bimetallic disk has a contact end with a contact superposed with a fixed contact of the fixed contact connection in such a way that a contact is established. When the contacts are opened, a spring-loaded isolating slide moves between the contacts. The isolating slide has an illuminated push button for reliably identifying a disconnection.