No sure what you're exactly asking as which light or what the lables mean.. but we'll solve the No One part. :stickpoke TC is tool changer. The lights are covered in the Electrical Service Manual and have the usual Schematics and diagrams. They are part of the I/O circuit and feedback signals. TC ok as Tool Changer OK. TC In.. then the changer has traveled in and made the limit switch etx. Helpful for diagnosis. Peace, GC