This shows how the sights are used to align the plotter to graph paper. The small sight is one inch above the pen and can be used to align the pen without removing it when using paper that has lines at multiples of an inch. For other paper the pen assembly is removed to use the larger sight. You can see the sight has a cross hair that would be aligned with the major division that is the origin of the graph using the manual movement switches. This allows the grid to be used to accurately read off points on the graph.
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