Abstract: A variable volume air conditioning system of the type having a duct for distributing air to a room, a damper for regulating the flow of air through the duct, and a damper actuator responsive to damper drive control signals for controlling the damper. A thermostat located in the room provides a stat signal representative of a desired flow of air through the duct. An actual flow signal representative of the actual flow of air through the duct is provided by a sensor. The stat signal and actual flow signal are compared by a comparator which provides the damper drive control signals as a function of the comparison. A wire transmission line couples the actual flow signal from the sensor to the thermostat so that service personnel can easily monitor system performance.

Abstract: A flat, elongate, laminated plate of ceramic piezoelectric material is fixedly mounted on one end to permit movement of the other end responsive to the application of a variable electronic control signal to electrodes on the outer surfaces of the laminated plate. The movement and force applied by the movable end of the plate controls the release of air pressure from the pressure chamber so that the pressure in the chamber varies in response to the variations of the electronic control signal.