This unit includes a flashing red LED to indicate the alarm is receiving power. The i9050 is UL Listed and includes a 10-year limited warranty. Battery operated (9-Volt battery included) provides continuous protection even during power failures. Test button verifies battery and alarm operation. Low battery indicator chirps when battery needs replacement. Easy installation no wiring required. Smoke detector utilizes an ionization sensor to detect fire hazards and sounds an 85 db alarm when a hazard is detected. UL/CSFM reference model i9050.