HomeSafe Wireless Outdoor Siren HomeSafe Wireless Outdoor Siren has 3 alarm functions; siren + LED, siren only, LED signal only Loud 120dB alarm turns on/off every 30 seconds when triggered until reset, to scare away intruders Ultra-bright LED flashing strobe light sends a warning signal when connected sensor detects movement Easy setup with the HA-SYSTEM or other HA sensors, which are required for the siren to operate Low battery indicator, quick wall mount and AC adapter or optional 4 AAA battery powered operation