Abstract: Both undervoltage and shunt trip auxiliary feature modules, adapted to be mounted side-by-side with one or more circuit breaker modules include an electromagnetic trip device having a trip actuator which is biased toward tripping position and is normally latched in a reset position. A lost motion connection interconnects the actuator with a trip member which is in direct driving engagement with the releasable latch for the automatic trip means of the circuit breaker so that when the actuator is released, movement thereof is transmitted through the trip member to the circuit breaker latch for tripping of the latter. Each auxiliary feature module also includes a reset member which acts to automatically reset the actuator after each tripping operation thereof. The reset member is in direct driving engagement with the cradle of the circuit breaker contact operating mechanism so that movement of the cradle towards its tripped position will operate the reset member in a direction to reset the actuator.