Completely self-contained. Fully Automatic Operation. Compact, low profile design in a neutral finish. Push to test switch. Automatic, low voltage disconnect (LVD). 120 or 277 VAC operation. Injection-molded, V-O flame retardant, high impact, thermoplastic housing. Charge rate/power on LED indicator light. Energy consumption of 3.2 watts for red letters and 3.8 watts for green letters.