Patent ID: 7377120

Claim:
A control associated with a first HVAC unit that is coupled to a common duct shared with at least one other HVAC unit, the control comprising: a twinning connection in communication with at least one other control associated with the at least one other HVAC unit; a low voltage signal applied to the twinning connection; a sensing means for sensing when the voltage at the twinning connection is being conducted to ground; a switching means for switching the voltage at the twinning connection to ground; and a microcomputer in communication with the sensing means and the switching means, the microprocessor being configured to actuate the switching means to switch the voltage at the twinning connection to ground for a predetermined time period to communicate a blower speed for the first HVAC unit, and to monitor the sensing means to determine the period of time that the voltage at the twinning connection is being conducted to ground which corresponds to a prescribed blower speed for each HVAC unit, wherein the microprocessor responsively controls the speed of the blower associated with the first HVAC unit according to the prescribed blower speed corresponding to the sensed period of time.