Two terminals and two terminals on the left or right of the double-pole double-throw switch connected with the knife are respectively connected with a power supply and an electric fan, and the two terminals on the left and the two terminals on the right of the double-pole double-throw switch are connected with each other, thereby changing the direction of current passing through the electric fan.
Scheme 1: Connect the power supply E with B and E; The electric fan f connects c and f; A is connected with F, and C is connected with D, as shown in the figure.
Option 2: electric fan f is connected to b and e; Power supply e is connected to a and d; A is connected with F, and C is connected with D, as shown in the figure.