This application is a Smith (transmission line calculator) chart. You may move around the chart by using the trackball or the d-pad to change the impedance or the reflection coefficient and distance to load. You may also change the impedance to an admittance, complement the reactance or set the real part of the impedance/admittance to zero (for stub matching). You may also go to the "g=1" circle along a constant reflection coefficient circle (for stub matching). A menu item "Double Stub" draws a rotated "g=1" circle and allows you to perform double-stub impedance matching. (Currently the separation between the two stubs is fixed at one-eighth of a wavelength.) When you press the g=1, button, you will go to this rotated circle. This circle will be rotated back (one-eighth of a wavelength) to the original g=1 position using the "rotate" button. Some impedance values do not allow for double-stub tuning, and these values are shown in gray. Should you change the impedance to any of these values, the "g=1" and "rotate" buttons will be deactivated. The precision of this application is only to two significant places. It is not intended to be a precise calculator, but rather a graphical tool to quickly perform rough calculations for transmission line problems. Currently, there is no numeric input--only the trackball/d-pad is used to change the parameter values. Changes (deltas) in reactance and distance to the load are displayed. When you select "Double Stub" from the menu, a selection menu for three different stub separations appears.