(a) Externally Illuminated Sign

Any sign which is illuminated by a light that reflects off the surface of the sign from an external source, shall be considered an externally illuminated sign.

(b) Internally Illuminated Sign

Any sign shall be considered an internally illuminated sign where the source of the illumination is inside the sign and light emanates through the message of the sign. Signs that consist of or contain tubes that are filled with neon or some other gas that glows when an electric current passes through it and are intended to form or constitute all or part of the message of the sign, rather than merely providing illumination to other parts of the sign that contain the message, also shall be considered internally illuminated signs.