Epson 10020 - Manual (Page 177)

If all eight pages are correct, press Y and Enter. If any page is
filled with an incorrect number, press N and Enter co display
the error message.
Light Pen Check
To check the function of a light pen connected to the color
graphics adapter card, press 8 and then Enter. This test checks
that a light pen connected to the color graphics adapter is
performing accurately. When you select this check, you see
these prompts:
Enter Y to start light pen check.
Enter N to return to the menu.
If you do not have a light pen attached, press N and Enter. T o
begin the test, press Y and Enter. You see this prompt:
PLACE LIGHT PEN ON CENTER OF WHITE BLOCK
Touch the center of the white block on the screen with the
light pen. When the light pen is correctly positioned, the block
moves to another part of the screen for a second teat. After
three successful tests, the check ends.
An error occurs if:
The light pen is not connected properly
You touch the screen at the wrong point
The light pen is malfunctioning
You do not touch the square within a certain amount of
time (which is dependent on the current CPU speed).
D-20 Performing System Diagnostics