The Honeywell 2012/24AUSI is designed to provide early warning of developing fires for occupants of residential and commercial buildings. The 2012/24AUSI is a photoelectric smoke detector that is specifically designed for open area protection. These multi-voltage, 4 wire smoke alarms can be connected to many third-party devices such as security alarm systems and access control systems. The 2012/24AUSI is supplied complete with mounting ring and 9VDC back-up battery.