DS-PDSMK-E-WEAX SmokedetectorChamber With Photoelectric SensorBuzzer = 85dB @ 3 mTransmission Method Two-Way RF WirelessTransmission Frequency 868 MHz10 years battery lifeStandard Battery Life10 years for standalone sensor 5 years for RF wirelessPower Supply Battery PoweredBattery Type:Non Replaceable Energizer L91 x 2 for Sensor Replaceable CR123A x 1 for RF Wireless