Is a device that senses smoke and start buzzing.
Tamper switch button.
Built-in buzzer alarms when detect smog density over the standard level (UI 217 / 3.2%/feet).
Makes alarm by itself via built-in buzzer and also send out the wireless alarm signal to alarm control panel at the same time.
Low battery indication that make once sound in each 2 hours via built-in buzzer.