the present invention will be apparent from the following detailed description , which proceeds with reference to the accompanying drawings , wherein the same references relate to the same elements . please refer to fig1 . in the drawing , z 1 is a bridge rectifier circuit . sw 1 is a forward / reverse controlling switch with an on or auto position , off position , and reverse position . sw 2 is a motor rotation speed switch with a fast and slow position . m 1 represents ac motor coils , including the rotor coil 202 , the stator coil 203 , and the auxiliary low - speed coil 201 . this preferred embodiment contains four operating circuits for the following four modes : forward fast , reverse fast , forward slow , and reverse slow . the first circuit is the forward fast mode . in this mode , the forward / reverse controlling switch sw 1 is switched to auto and the motor rotation speed switch sw 2 is switched to fast . in this case , the ac current flows through the bridge rectifier z 1 and gets converted into a dc current . the dc current enters the sixth pin of the forward / reverse controlling switch sw 1 . it is then output via the fifth pin of the forward / reverse controlling switch sw 1 to the second pin of the motor rotation speed switch sw 2 . afterwards , it is output via the fourth pin of the motor rotation speed switch sw 2 to the fourth pin of the ac motor stator coil 203 . the current is then output by the third pin of the ac motor stator coil 203 to the first pin of the forward / reverse controlling switch sw 1 . afterwards , the current is output from the first pin of the forward / reverse controlling switch sw 1 to the sixth pin of the ac motor rotor coil 202 . finally , the current flows via the fifth pin of the ac motor rotor coil 202 back to the bridge rectifier z 1 . this completes the circuit for the forward fast mode of the motor . the second circuit is the reverse fast mode . in this mode , the forward / reverse controlling switch sw 1 is switched to rev and the motor rotation speed switch sw 2 is switched to fast . in this case , the ac current flows through the bridge rectifier z 1 and gets converted into a dc current . the dc current enters the seventh pin of the forward / reverse controlling switch sw 1 and leaves via the eighth pin of the forward / reverse controlling switch sw 1 to the third pin of the ac motor stator coil 203 . afterwards , it is output via the fourth pin of the ac motor stator coil 203 to the fourth pin of the motor rotation speed switch sw 2 . it is then output via the third pin of the motor rotation speed switch sw 2 to the fourth pin of the forward / reverse switch sw 1 . afterwards , the current is output by the third pin of the forward / reverse switch sw 1 to the sixth pin of the ac motor rotor coil 202 . finally , the current flows from the fifth pin of the ac motor rotor coil 202 back to the bridge rectifier z 1 . this completes the circuit for the reverse fast mode of the motor . when the rotation is reversed , the direction of electrical current flowing through the stator coil 203 is opposite to that in the forward mode . on the other hand , the direction of electrical current flowing through the rotor coil 202 is invariant in the forward and reverse modes . the third circuit is the forward slow mode . in this mode , the forward / reverse controlling switch sw 1 is switched to auto and the motor rotation speed switch sw 2 is switched to slow . in this case , the ac current flows through the bridge rectifier z 1 and gets converted into a dc current . the dc current enters the sixth pin of the forward / reverse controlling switch sw 1 . it is then output via the fifth pin of the forward / reverse controlling switch sw 1 to the second pin of the motor rotation speed switch sw 2 . afterwards , it is output via the first pin of the motor rotation speed switch sw 2 to the first pin of the ac motor auxiliary low - speed coil 201 . the current is then output by the second pin of the ac motor auxiliary low - speed coil 201 to the fourth pin of the ac motor stator coil 203 . the current is output by the third pin of the ac motor stator coil 203 to the first pin of the forward / reverse controlling switch sw 1 . afterwards , the current is output from the second pin of the forward / reverse controlling switch sw 1 to the sixth pin of the ac motor rotor coil 202 . finally , the current flows via the fifth pin of the ac motor rotor coil 202 back to the bridge rectifier z 1 . this completes the circuit for the forward slow mode of the motor . in the low rotation speed mode , the electrical current flows through the motor rotation speed switch sw 2 and enters the low - speed coil set inside the motor . due to its partial voltage and current restriction , the rotation speed of the motor slows down . the fourth circuit is the reverse slow mode . in this mode , the forward / reverse controlling switch sw 1 is switched to rev and the motor rotation speed switch sw 2 is switched to slow . in this case , the ac current flows through the bridge rectifier z 1 and gets converted into a dc current . the dc current enters the seventh pin of the forward / reverse controlling switch sw 1 . it is then output via the eighth pin of the forward / reverse controlling switch sw 1 to the third pin of the ac motor stator coil 203 . it is then output via the fourth pin of the motor stator coil 203 to the second pin of the ac motor auxiliary low - speed coil 201 . the current is then output by the first pin of the ac motor auxiliary low - speed coil 201 to the first pin of the motor rotation speed switch sw 2 . the current is output by the second pin of the motor rotation speed switch sw 2 to the fourth pin of the forward / reverse controlling switch sw 1 . afterwards , the current is output from the third pin of the forward / reverse controlling switch sw 1 to the sixth pin of the ac motor rotor coil 202 . finally , the current flows via the fifth pin of the ac motor rotor coil 202 back to the bridge rectifier z 1 . this completes the circuit for the reverse slow mode of the motor . in the low rotation speed mode , the electrical current flows through the motor rotation speed switch sw 2 and enters the low - speed coil set inside the motor . due to its partial voltage and current restriction , the rotation speed of the motor slows down . although the invention has been described with reference to specific embodiments , this description is not meant to be construed in a limiting sense . various modifications of the disclosed embodiments , as well as alternative embodiments , will be apparent to persons skilled in the art . it is , therefore , contemplated that the appended claims will cover all modifications that fall within the true scope of the invention .