Before installing DC power supply units in your switch, perform these steps:
        
        - 
                Verify that the DC circuit is de-energized.
            
- 
                Identify the grounding lug on
                    the rear of the switch.
                The grounding lug is identified
                    by the international symbol for earth ground:   
- 
                Attach the ground wire to the
                    grounding lug as follows.
                Use stranded copper wire, sized
                    between 14 AWG and 6 AWG. 
                    - 
                        At one end of the ground
                            wire, strip the insulation to expose 12 mm (1/2 in) of bare wire.
                    
- 
                        Insert the stripped wire
                            into the grounding lug.
                    
- 
                        Using a straight-tip
                            torque screwdriver, tighten the retaining screw to 2.25 N m (20
                            in‑lb).
                    
 
- 
                Connect the other end of the
                    wire to a known reliable earth ground point at your site.
            
You can now install one or two DC power supplies, following the steps in Install a 750 W DC Power Supply.