The versatile and reliable NB 728 Stand-alone photoelectric smoke detector is under VdS approved, and can be calibrated into either UL, BSI Standards. It features UL-approved Photoelectric sensing components with precise smoke detection. and long life (18 months) 9V battery operation (9V Ultralife Lithium battery model for 7-year life is available too). NB-728 also comes with optional heat detection combo model and various power input.