This is an independent photoelectric smoke detector fire alarm. It is designed for residential safety to detect smoldering fires early and sound a local audible alarm. 
Included Components;

Smoke Detector Unit: The circular main body with a built-in sensor chamber, a test button, and status indicator LEDs.

Batteries: Two AA batteries used to power the device independently without external wiring.

Mounting Hardware: Two plastic wall anchors and two matching screws for secure ceiling installation. 

Key Specifications & Features;

Detection Principle: Photoelectric sensing technology optimal for detecting slow, smoldering fires.

Alarm Volume: Emits a loud, piercing audio alert (typically around 85 decibels) to awaken residents.

Test Functionality: Features a "TEST" button on the face to regularly check the circuitry and siren function.