General term for any type of electronic programmable sign. Often called electronic displays or electronic changeable copy signs, the content of electronic message centers is changed or altered via electrically illuminated or mechanically driven changeable segments. Electronic message centers may project still images, scrolling images or moving images, including video and animation. Fixed message electronic displays have preprogrammed informational content, while computer controlled variable message electronic displays have content that can be changed or altered by computer driven electronic impulses.