Abstract: A double hung window has upper and lower window sashes in a window frame including a header, sill, and a vertical jamb on each side. The upper sash is pivotally connected to the frame header for inward pivotal movement on a horizontal axis. The lower sash is pivotally connected to the upper sash for reverse pivotal movement on a parallel horizontal axis, whereby to fold the lower sash up and under the upper sash. A tape balance atop the frame applies a lifting force to the lower sash. Grasp and inward pull of a handle pulls lower and upper sashes inward from a dead center condition, thereby enabling the tape balance to effectively assist in pulling the sashes upward. A screen, separate from the window sashes, is removably mounted on the outer face of the window frame.

Abstract: An apparatus and method of calibrating a digital to analog converter including means for establishing and storing a minimum and maximum analog endpoint value slightly in excess of the desired operating range of the DAC and then scaling each respective raw data point of the DAC within the established endpoint values.