3. The system of claim 2 , wherein the pattern comprises lines visible on the display screen, each line within an excon image of a similar type and spaced from the other lines within that excon image.
3. The system of claim 2 , wherein the pattern comprises lines visible on the display screen, each line within an excon image of a similar type and spaced from the other lines within that excon image. 4. The system of claim 3 , wherein the lines within at least one excon image are solid and the lines within another excon image are dashed.