During Bob Lazar's work at S4 he had a chance on at least one occasion to go inside the disc while entergized.  From what we are told this is what he encountered on one wall.

At a certain point when the disc was energized, a form of writing appeared on the right side of the archway directly in front of the seats. The remainder of the metalic archway face became transparent, exposing the exterior view from that angle.

Note the seating pattern in the illustration above. The black area would indicate the area outside the disc which became transparent to the occupants of the seats. The blue sidebar would remain and a light horizontal bar would scroll up or down the lines of text. Illuminating the pattern as illustrated. Take special note to the alternating slant of every other line. The writing were forms like these with "eyes" or subcircles within the circles and elipses. It was not explained to Lazar how this interface was actuated, except for seeing technicians switching it on from a hole in the floor of the centerlevel main deck. A hole where one of the gravity amplifier heads was cut out.