Greenheck model SQ-95-D-X

A Greenheck inline fan was found installed in the attic of a 2005 build. The fan appeared to be attached to the HVAC duct work. The duct supply registers were mounted in the ceiling with a remote controller mounted on the wall of the master bedroom closet. First one I have ever observed. What is the purpose of the fan?

Model# SQ-95-D-X