Wireless indoor smoke and heat detector with sounder, Sensing element: Photoelectric and temperature sensors, Activation threshold: +59°С ±2°С, Type of notification: Sound/light, Volume of built-in siren: 85 dB, Alarm signal delivery time: 0.15 s, Power supply: Battery: Two CR2 batteries, 3 V Backup battery: CR2032, Battery life: Up to 4 years.