"GPC failure votes are annunciated in a number of ways. The GPC status matrix on panel O1 is a 5-by-5 matrix of lights. For
example, if GPC 2 sends out a failure vote against GPC 3, the second white light in the third column is illuminated. The yellow
diagonal lights from upper left to lower right are self-failure votes. Whenever a GPC receives two or more failure votes from
other GPCs, it illuminates its own yellow light and resets any failure votes that it made against other GPCs (any white lights in its
row are extinguished). Any time a yellow matrix light is illuminated, the GPC red caution and warning light on panel F7 is
illuminated, in addition to master alarm illumination, and a GPC fault message is displayed on the CRT. "
Acknowledgement: NASA Shuttle Reference Pages
