Smoke Alarm Detection Method Ionization Up to 18 Units Interconnection Capability Power Source 120V AC 9V Audible Alert 85 dB @ 10 ft Visual Alert Style LED Diameter 5 1/2 in Height 2 in Width - Digital Readout No Battery Backup Yes Hush Button Yes Locking Pin Yes Operating Temp 40 Degrees to 100 Degrees F Standards UL217 CSFM NFPA72 HUD FHA Manufacturers Warranty Length 10 yr Limited Battery Location Side