Dual power Automatic fer switch can switch to Normal power or reserve power automatically. Please noted that the switch can't turn on or turn off the generator. This switch Normal power first. If normal power on, the switch switch to Normal power. If normal power off, and reserve power on, the switch switch to reserve power. the button to Automatic, the switch switch to Normal power or reserve power automatically. the button to Manual, Then you have to switch the Direction manually. Noted: power be interrupted when Switching. TOQ3D is terminal type automatic fer device. It's suitable for 3 phases 4 wires (or 1 phase 1 wire) dual power grid with AC 50/60Hz, rated voltage 400V/230V and rated current up to 63A. When one power goes wrong (only test normal Phase A voltage and reserve Phase A voltage, only test loss voltage or loss phase),it automatic connect one or several load circuits from one power to the other power automatically, to normal power supply of load circuits. The automatic fer switch conforms to IEC60947-6-1 and GB/T14048.11 Colour:white Material:ABS Size:150*138*111mm Package Contents: 1*Dual power automatic fer switch Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.