TR symbol on residential receptacles assures they meet the 2008 NEC requirement * A shutter mechanism inside the device blocks access to the contacts unless a two-prong plug is inserted, helping ensure foreign objects will be locked out. * Patented lockout feature for added safety prevents RESET if GFCI is not operating properly * Advanced electronics design provides superior resistance to electrical surges and over-voltages * Expanded wiring options with eight back-wire holes (two for each line and load connection) plus ground with an internal clamp