AFCI and/or GFCI units (10) with onboard trip monitoring and/or wiring error monitoring circuit (100) with an opto-isolator (50) and a controller (60) in electrical communication with the opto-isolator (50). The controller (60) monitors the opto-isolator (50) to identify a TRIP or RESET state of the circuit (100) such as one associated with a receptacle and/or a wiring error of the unit (10), e.g., receptacle.