Smoke Alarm, Detection Method Photoelectric, Up to 24 Units Interconnection Capability, Power Source 120VAC, 9V, Audible Alert 85dB @ 10 ft., Horn, Visual Alert Red LED, Diameter 5-5/8 In., Height 1-1/2 In., Width -, Digital Readout No, Battery Backup Yes, Features Quick Connect Power Harness, Hush Button No, Locking Pin Yes, Operating Temp. 40 to 100 Degrees F, Standards UL, NFPA, Federal Housing Authority, Housing and Urban Development and California State Fire Marshal Guidelines Smoke and Combination Smoke/CO AlarmsInterconnectableSmoke AlarmsTest/Reset button test11s alarm circuitry, alarm activation, and battery function. Several models include a hush button to silence nuisance alarms. 85dB horn. Easy installation. Operating temp.: 40 to 100 F. 120VAC, 60 Hz.Alarm Types: Ionization respond best to fast-raging fires. Photoelectric respond best to slow-smoldering fires. All interconnect units must interface directly with their own brand of interconnectable smoke and CO alarms.Feature green LED power-on indicator and red LED indicator when alarm is activated. Latching alarm identifies initiating alarm. Locking mechanisms lock the battery drawer and secure alarm to base, except 1XTG5 and 1XTG8 include optional locking mechanism that deters removal of unit. 3YNJ1 has a sealed, rechargeable battery backup.Meet UL, NFPA, FHA, HUD, CSFM standards