Abstract: A two-pole miniature circuit breaker is configured for calibration of both pole mechanisms with the circuit breaker fully assembled. The identical pole mechanisms are mounted in the same orientation in parallel outer compartments of a molded housing with the metal support frame of one pole against the outer housing wall and the frame of the other spaced from the associated outer wall. A coupler couples the two-pole mechanisms together for simultaneous opening of both poles when either pole is tripped has an actuating member on each end which engages the trip device of the associated pole. The actuating member, at least of the pole with the metal frame spaced from the housing outer wall, is configured to provide direct access for a calibration tool inserted through a calibration opening in the housing to engage a calibration slot in the metal frame.

Abstract: Miniature circuit breaker apparatus is taught which includes side-by-side ganged cases where one of the ganged cases includes the main circuit breaker operating mechanism and contacts and where the other case includes an actuable micro-switch, which is interconnected with an indicating device for providing either a bell alarm function for the circuit breaker system or an auxiliary switch function for the circuit breaker system. The bell alarm function is provided by extending the rotatable axis of the trip mechanism of the main circuit breaker into the case of the secondary circuit breaker casing for movement of an auxiliary switch. The auxiliary switch indicates a trip function when the main circuit breaker contacts have been tripped opened, thus providing a bell alarm indication, for example.