Wiring Diagram Lighting Circuit Joint Box Method - Great for Wiring to LED Downlights (Spotlights) Student training aid for the connections required to wire a lighting circuit using the joint box method. Video explains the connection required within the the lighting point, a consumer unit (fuse box) and in 1 way switch. The circuit is wired in twin and CPC cables (twin and earth cable) and is a wiring diagram for this circuit. This video will show learners how to connect up a joint box to feed t