An emergency lighting function illumination appliance comprised of a fluorescent lamp tube, a controller, a mains power circuit capable of processing mains electric power for lighting, and a backup circuit that provides for a backup power source. With these devices combined, the controller produces the following functions: 1) When mains power is normally supplied, an ON-OFF switch approach controls the fluorescent lamp in accordance with user intent. 2) During a mains power outage, the power circuit is automatically shifted to the backup circuit and the backup power source supplies electricity for emergency lighting. 3) When mains power supply is restored, the power circuit is automatically shifted to the mains power circuit and the mains power resumes the ordinary lighting function.