The 7139Ls is a 120VAC with 9Vdc battery back-up photoelectric smoke alarm designed to give reliable early warning of the presence of smoke where both audible and visual alarms are required. The 7139Ls a 9-foot plug-in line cord for ease of installation in any space where a visual alarm is required. Fully insect screened. . 120 vac with 9Vdc battery back-up . 90Dba temporal 3 evacuation piezo horn with 3100Hz (nominal) horn frequency . On-site washing program . Nominal 2. 5% sensitivity . 3 position test switch . Low or missing battery indicator . 9′ plug-in line cord . 1 year warranty from date of purchase.