20A feed-through: that is the input and output power allowed max-current is 20A .( constant voltage) 15A receptacle outlet : duplex 5-15R American standard receptacle on the surface work as one of power output.(another one is the power output) End-of-life light: with inner system self- diagnosis ability, checking the internal main electronics operation condition of spare part always. If occur damage or lose function, will bright the end-life light to invite user to process. Operation indicator light : green indicator will bright when GFCI switch on, when it is of disconnection, the light will quenched. UL943-2006 standard is GFCI latest version standard, this specification is tested by the UL943-2006 standard and gained the UL and CUL certification.