Systems, methods and devices are described that provide a three-state control signal across a single electrical conductor. A three-position switch provides an output signal that selects between the first reference voltage, a second reference voltage and an intermediate voltage. The output from the switch is transmitted to a voltage divider circuit that produces a predetermined result when the switch output corresponds to the intermediate state. The output of the voltage divider is then provided to an analog-to-digital converter to decode the state of the switch. The three-state control signal may be used, for example, to place a vehicle component such as a windshield temperature controller or rear-window defogger into a desired one of three operating states. Similarly, the three-state concepts may be widely applied in many automotive, industrial, consumer electronics and other settings.