Hess screen comes in wooden frame with points illuminated with red LED’s. The control unit has buttons which illuminated the LED’s as the buttons are pressed.
Electric Hess Screen This rigid matte grey Hess screen is feint marked with intersecting parabolae at each 5° generated for use at 50cm. A red LED is situated at each of the cardinal points at the 15° and 30° intersects. There is a corresponding array of buttons on the BOX , so that when a button is pushed the selected LED lights up.