The detector is a photodetector that uses the most advanced optical sensing chamber. The detector is designed to provide open area protection without wiring and easy to install and construct; The red LED on each detector provides a local 360° visible alarm indication. They flash once every minute, indicating that the power is on and the detector is working. When an alarm occurs, the red LED is on; when the battery is low, the red LED will flash and will beep. The red LED will be on when the fire alarm is activated, until the smoke concentration is lower than the alarm threshold. The test button is used to test whether the detector works normally; each time the buzzer is pressed, the buzzer emits a beep, the red LED flashes, and simulates a fire alarm; this button can be used for local mute during a fire.