Abstract: A thermally responsive damper assembly for mounting into a duct which is to be regulated by the damper assembly comprises a damper plate having oppositely disposed notch portions and arm portions one piece with said damper plate projecting outwardly in said notch portions and thermally responsive convoluted coil elements having convolutions surrounding said arm portions, bracket means affixed to the outermost convolution of each of said coil elements for attachment to said duct, and each of said coil elements having innermost convolutions keyed for attachment in only one orientation to an arm projecting outwardly in a notch portion of said damper plate.

Abstract: A motor control circuit utilizes sample and hold circuitry whose operation is initiated by an analog switch to control the firing angle of silicon control rectifiers, thereby to minimize wasting of power supplied to the motor being controlled.

Abstract: A thermally responsive damper for operation in a rectangular ventilation duct.

Abstract: An automatic flue damper positioned respectively to open and closed positions by means of motive apparatus, such as a solenoid motor, is provided with mechanical means for automatically latching the damper in its open position.