Upper incoming line, lower outgoing line, main circuit on the left, control circuit on the right, horizontal and vertical. The exposed laying can take the sheath line, or through the pipe and trunking. A distribution board or distribution box is where the main power supply is distributed to multiple loads. And all the switching and protective devices are installed in the. Exposed electrical wires present a serious hazard, creating immediate risks of electric shock and fire from short circuits or arcing. However, the key to. Connection method: Each switch takes a wire from the incoming point and connects it to the incoming end of the switch, or uses parallel connection to reduce the difficulty of wiring.