HomeSafe Wireless Outdoor Security Siren has a 120db high output alarm. It has 3 alarm functions: siren + signal light, signal light only, siren only, delay timer 0-10s. It can be used as a siren alarm with the HA-SYSTEM. The Siren can also be used as a stand-alone siren by connecting up to 8 additional sensors, HA-MOTION, HA-SENSOR, HA-MOTION-OD. Once one of these sensors detects motion it will sound the alarm. The siren has an automatic shut off. Every 30-seconds the alarm will turn on and off once the alarm is triggered until its reset. The siren comes with a power adaptor and wall mount. It works with 4, AAA batteries (not included).