Features:  Smoke alarm detector (433 smoke alarm detector, can be used with Sonoff RF bridge 433 to realize APP alarm after smoke fire. Through the scene, alarm can be set to link other eWelink switches).    Note: not include battery, battery model (9V 6F22).    Specifications:  Weight: 128g;  Packing size: 11*10*4cm;    1. 3 seconds alarm, sensitive response, using infrared scattering principle, fire smoke alarm for about 3 seconds, timely alarm, reduce your property loss to controllable range.  2. Sound and light alarm, when the smoke reaches the predetermined value, the indicator light flashes quickly and emits a green light prompt, and the smoke alarm alarm sounds about 110 decibels.  3. 360-degree smoke detection alarm, no dead angle, reliable.  4. Built-in 110 decibel sound and light alarm prompt, effective prompt evacuation site, built-in high sensitivity sensing technology, reliable, safe.  5. Suitable for a variety of scenarios, independent type does not require an external power supply, suitable for families, hotels, office buildings, factories, etc.    Package included:  3 x 433MHz Smoke alarm detector;  3 x English User manual;  6 x Screw caps;  6 x Fixing Screws