230V Smoke Alarm Mains Power DHI-HY-SA5MA with 10 Year Rechargeable Lithium Back-up Battery is specifically designed to continuously monitor smoke concentration. Adopting advanced split-spectrum photoelectric chamber and a built-in high-volume buzzer, it responds quickly and becomes highly sensitive with stable performance and low false alarm. Once the surrounding smoke concentration reaches the alarm value, it will promptly send out visual and audible alarm signal to remind the user to take immediate measures. Smoke alarm can be interconnected via a hardwired or wireless system (using optional WisuLink wireless interconnected module). Once one device triggers an alarm, the alarm signal will be pushed to every alarm in the interconnected network and they will raise the alarm in unison.