*1.5V AA battery *Electrochemistical CO Sensor *3 digits LCD displayer *Low bat and malfunction Indicator *CE, TUV EN50291 LCD display Carbon ... RCC426B,TUV EN50291 certificate Specification:* Power Supply: 3*1.5V AA batteries, if you need AC Power carbon monoxide detector, link here ... 4 times with unit chirping every 5 seconds, then repeat* Low-bat Indicator:Chirp every 30s as battery lower than 3 ...