Please Note: Because of shipping limitation, battery( DC9V 6F22 ) for smoke detector not included. Features: *Support three alarms: independent sound & light flash alarm, wireless 433 transmission network alarm. *360 degrees smoke detection and alarm, no dead angle, reliable. Built-in 90 dB sound and light alarm reminder, effectively prompting people to evacuate. *Adopt high-performance photoelectric two-way scattering patented technology of two-receiving & one-transmitting and high-sensitivity sensing, stable, reliable, safe and accurate. *This smoke sensor can work alone to realize independent alarm at home. To achieve remote control on the phone, smoke detector needs to work with Sonoff RF bridge( 433Mhz, EV1527) host. *Ultra-low-power microcontroller + photoelectric principle technology, long standby life battery use for 3 years. *Low Voltage Alarm: When the battery voltage is lower than 6.8V, a warning sound is issued to remind the user to change the battery. *Full snap-in patented structure, simple installation, no need for debugging and wiring. Convenient for cleaning and battery replacement. Specifications: Power Supply: DC 9V 6F22 alkaline battery (not included) Standby Current: 10uA Alarm Current: 100mA Alarm Indication: Sound alarm & LED flash Sound Level: 90dB/3M Detecting Area: 20 square meter Wireless Frequency: 433MHz APP: eWeLink Operating Temperature: -10C ~+50C Operating Humidity: 95% RH Item Size: Approx. 10.5 * 10.5 * 3.5cm (L*W*H) Package Information: Package Size: Approx. 10.5*10.5*3.8cm / 4.1 * 4.1 * 1.5in Package Weight: Approx. 120g / 4.2oz Package List: 1* Wireless Smoke Detector 1* User Manual (English) Return Policy All of our items come with a 30-day free return policy. If you need to return, please contact us, let us know the detailed problem and send us some pictures for confirmation. We reserve the right to refuse any returns for objective reasons. Shipping Policy All of our items are shipped free with tracking numbers. Orders will be shipped within 3 working days upon receipt of payment. Most orders will be shipped within 1 working day. In most cases, shipping takes 8-12 working days.