1. There are three major screens in the application. ACE-HF opens with the Main Screen, on which the primary point-to-point circuit appears. When you place the mouse cursor over the transmit or receive dot a hint appears giving the latitude/longitude of the terminal, the distance between the two points and the path heading from one terminal to the other. Distance units in km, miles or nautical miles are selectable. After a circuit prediction is made, the "Open Bands Boxes" in the upper right corner show which bands are "open" (green) at the current time. The Main Screen provides navigational controls to other ACE-HF features, including those of this screen. You can place up to nine additional circuit paths on the Main Screen, as well as Range Curves, curves showing Line-of-Sight limits (including satellite footprints), labels and symbols. For example, you might construct a Main Screen diagram to depict the various circuits of a favorite HF network. This example shows a family of range curves at 2500-km intervals.