based on which of the temperature and non temperature parameters requires greater change freeze protection and maximum and minimum damper position circuits override the basic damper control signal to avoid excessively low space temperatures and to provide air exchange limits application_number US 23544399 A description in the following detailed description references are made to the accompanying drawings which form a part hereof an in which is shown by way of illustration specific embodiments in which the invention may be practiced these embodiments are described in sufficient detail to enable those skilled in the art to practice and use the invention it is to be understood that other embodiments may be utilized and that electrical logical and structural changes may be made without departing from the spirit and scope of the present invention the following detailed description is therefore not to be taken in a limiting sense the scope of the present invention is defined by the appended claims and their equivalents in fig1 reference 10 generally identifies apparatus for conditioning air within an enclosed space the apparatus including a duct system 12 for supplying conditioned air to and exhausting air from the space a supply duct 13 is shown housing a fan or blower 14 for circulating air through duct system 12 and the enclosed space a heating heat exchanger 16 and cooling.