Systems and methods for conveying information using a control signal referenced to alternating current (AC) power

A lighting system, comprising:

• an alternating current (AC) power supply;
• a controller connected to the AC power supply and comprising:
• a drive circuit within the controller for driving a single wire with a pulse width modulation (PWM) signal based upon a desired lighting output level, the PWM signal having a high voltage and a low voltage, the high voltage being greater than a voltage midpoint that is substantially midway between potentials of power lines of the AC power supply, and the low voltage being lower than the voltage midpoint;
• at least one lighting unit, each lighting unit connected to the AC power supply and
• the single wire and comprising:
• at least one light emitting device;
• a lighting control circuit for controlling light output of the at least one light emitting device;
• a reference circuit for generating a comparison voltage by dividing substantially midway the potentials of the power lines of the AC power supply;
• and
• a compare circuit coupled with the single wire from the controller, for comparing the PWM signal received therefrom to the comparison voltage to determine low and high states of the PWM signal, the low and high states being input to the lighting control circuit to control the light output of the at least one light emitting device based upon the desired lighting output level.