Patent ID: 7922100

Claim:
A ground wire adaptor for connecting an environmental control, having a power terminal, a ground terminal, a control output terminal and a conductive element connected between the ground terminal and the control output terminal, to a heating/ventilating/air-conditioning (HVAC) equipment, having a first transformer output terminal, a second transformer output terminal and a control input terminal, via a two wire conductor, having a first wire and a second wire, the ground wire adaptor comprising: a first transformer input terminal connected to the first transformer output terminal for receiving a low-voltage alternating current and connected to the power terminal via the first wire; a second transformer input terminal connected to the second transformer output terminal for providing a ground return path; an EC terminal connected to the ground terminal via the second wire for providing a ground path; an asymmetrically-resistive electrical network connected between the EC terminal and the second transformer input terminal, providing a relatively lower resistance to current flow from the EC terminal to the second transformer input terminal and a relatively higher resistance to current flow from the second transformer input terminal to the EC terminal, for providing ground path continuity; a HE terminal connected to the control input terminal for providing a control signal; a control logic unit for sensing voltage on the EC terminal and responsive to detecting a negative half-cycle providing a control signal; a switching device for connecting, responsive to the control signal from the control logic unit, the first transformer terminal to the HE terminal to provide the control signal to the HVAC equipment; wherein a low-voltage alternating current half-cycle control signal is provided at the control output terminal of the environmental control when a function is being demanded and further wherein responsive to a control signal at the control input terminal, the HVAC equipment provides the demanded function.