Abstract: An electrical distribution system comprises a wiring module and a functional module. The wiring module mounts within an electrical box and has a functional side and a wiring side. The functional module has a front side and a back side and removably installs in the wiring module functional side. A key extends from, and is positioned on, the back side so as to identify a type of functional module. An aperture is positioned on the wiring module functional side so as to accept the key only when the functional module is properly oriented with respect to the wiring module. The wiring module is mounted within the electrical box according to the functional module type.