a circuit interrupting device having an auto - monitoring circuit for periodically testing various functions and structures of the device . the auto - monitoring circuit initiates an auto - monitoring routine which , among other things , generates a self - test fault condition and determines whether the detection mechanisms within the device properly detect the self - test fault . processing an early detection signal determines whether the self - test fault was properly detected without interfering with the normal operation of the detection circuitry and without causing a false trip within the device . additional functionality of the auto - monitoring circuit permits automatic verification that the device is properly wired , that is , not miswired , and determines whether the device has reached the end of its useful life .