Ground wire adaptor

A ground wire adaptor for providing a plurality of control signals to a heating/ventilating/air-conditioning (HVAC) equipment, having a first transformer output terminal, a second transformer output terminal and a plurality of control input terminals, and for connecting to both ends of a two wire conductor, having a first wire and a second wire, connecting a first location and a second location, the ground wire adaptor comprising:

• a multi-function environmental control, at the first location, having:
• a power terminal connected to the first wire for receiving a low-voltage alternating current;
• an output terminal connected to the second wire for establishing a ground reference for the multi-function environmental control;
• a control logic unit for continuously generating a control bit stream having repeated frames of N+1 bits, a first synchronizing bit of each successive frame alternating between values ‘0’ and ‘1’, each of the subsequent N bits in each frame taking on a value ‘1’ when a corresponding HVAC equipment function is being demanded and taking on a valve ‘0’ when the corresponding HVAC equipment function is not being demanded;
• and
• a switching device connected between the power terminal and the output terminal for receiving the control bit stream and responsive to each bit in the bit stream operating into a non-conductive mode when the bit has value ‘0’ and operating into a conductive mode when the bit has value ‘1’ thereby generating a control signal at the output terminal;
• and
• an adaptor module, at the second location, having:
• 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;
• a EC terminal connected to the output terminal via the second wire for providing a ground path and for receiving the control signal;
• 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 plurality of HE terminals, each connected to a corresponding control input terminals;
• a plurality of switching devices each one for connecting the first transformer terminal to a corresponding HE terminal responsive to a function control signal;
• a control logic unit for sensing voltage on the EC terminal and for:
• detecting the presence or absence of negative half-cycles and associating a ‘0’ value with the absence of a negative half-cycle and associating a ‘1’ value with the presence of a negative half-cycle;
• detecting successive frames by identifying the synchronizing bit and associating each of the subsequent N bits in each frame with a corresponding function control signal;
• asserting a function control signal to each of the switching devices to enter a conductive mode of operation when the corresponding function control signal has value ‘1’;
• and
• de-asserting the function control signal to each of the switching devices to enter the conductive mode of operation when the corresponding function control signal has value ‘0’;
• wherein a function control signal is provided at each of the HE terminals of the adaptor module when a corresponding function is being demanded and wherein, responsive to the function control signal at the corresponding control input terminal, the HVAC equipment provides the demanded corresponding function.