This versatile NB739 stand-alone photoelectric residential smoke alarm is VdS approved (Germany). It can be calibrated to either UL, BSI or VdS requirements. It features VdS and UL-approved photoelectric sensing components with precise smoke detection and a long life operation (2 years life with a 9 V common alkaline battery) or (10 years with 9 V Li battery ). Russian standard model available too.