*1.5V AA battery *Electrochemistical CO Sensor *3 digits LCD displayer ... RCC426B,TUV EN50291 certificate Specification:* Power Supply: 3*1.5V AA batteries, if you need AC Power carbon monoxide ... repeat* Low-bat Indicator:Chirp every 30s as battery lower than 3.3V with green LED flashing ... 0.2kg* Comply With: CE, TUV EN50291 Battery Operated LCD display Carbon Monoxide Detector(RCC426B ), TUV EN50291