An enhanced control mechanism for an LED light string system is provided for switching between one of two DC output phases or polarities so as to actuate one or the other of two LEDs within the bulbs on the light string. The control mechanism is further configured to allow switching so as to pass through the input power provided by a light string that is plugged into its electrical power feeding end. The control mechanism may provide either AC, rectified AC, or DC voltage of various values to the LED string according to the particular needs of the LED bulbs.